Clark v Ryan [1960] HCA 42; (1960) 103 CLR 486 (5 July 1960)

HIGH COURT OF AUSTRALIA

CLARK v. RYAN [1960] HCA 42; (1960) 103 CLR 486

Evidence

High Court of Australia
Dixon C.J.(1), McTiernan(2), Fullagar(3), Menzies(4) and Windeyer(5) JJ.

CATCHWORDS

Evidence - Expert witness - Qualifications - Opinion evidence - Principles governing admissibility - Evidence wrongly admitted - New trial.

HEARING

Sydney, 1960, April 1;
Brisbane, 1960, July 5. 5:7:1960
APPEAL from the Supreme Court of New South Wales.

DECISION

July 5.
The following written judgments were delivered:-
DIXON C.J. The questions upon which this appeal depends are the collision on the highway between two motor vehicles, and, if the evidence be inadmissible, the consequences upon the validity of the verdict of erroneously admitting it. (at p489)

2. The accident upon the highway occurred on 8th September, 1955. It was in broad daylight but on a drizzly day at a place called Piles Creek some miles south of Gosford on the Pacific Highway. Ryan, who is the plaintiff-respondent, was driving a panel-van northwards. Clark, the defendant-appellant, was driving a semi-trailer southwards. It was an articulated vehicle about six tons in weight unladen and forty-five feet in length. The prime-mover ran on two wheels at the front and two double wheels at the back and the trailer on two double wheels at the back. As the two vehicles approached the respective speeds as estimated in the evidence were thirty to thirty-five miles per hour for the semi-trailer and thirty miles per hour for the panel-van. At a bend in the road involving a left-hand swing for the semi-trailer and a right-hand movement for the panel-van, as they were nearing one another the semi-trailer "jack-knifed"; that is to say, instead of following the prime-mover round the bend in an apparent curve, it and the prime-mover took the form of a half-open clasp knife, the right-hand corner of the tray of the semi-trailer coming across the centre of the road well upon the wrong side of the road. Ryan in his panel-van in an attempt to avoid it ran off the bitumen into the channelling on his left; but the right-hand side of his van hit the right-hand corner of the semi-trailer and he was seriously injured. The plaintiff's case was that having regard to the nature of the defendant's vehicle, the wet roadway and the approach of the plaintiff's van, the defendant attempted to turn round the bend at an excessive speed. The defendant's case was that there had been a film of dust on the road surface at that place which became in consequence very slippery, once it was wet with the rain, causing him to go into a skid and that his speed was not excessive. The jury found for the plaintiff and the Supreme Court dismissed an application for a new trial by the defendant. From the order dismissing his application the defendant now appeals as of right to this Court. (at p490)

3. In the course of his charge to the jury Maguire J. before whom the action was tried, referred to the evidence given by a Mr. Foster Joy who was called on behalf of the plaintiff as an expert witness. His Honour said in effect that according to that evidence, if the jury accepted it, such a vehicle as the defendant's has particular characteristics one of which is that in taking a bend it has a tendency to swing out: in other words there is a time lag between the alteration in the direction of the prime-mover and of the trailer. If that was so the jury might take the view that the exercise of reasonable care required a different handling perhaps for such a vehicle, a greater degree of care than would be called for in driving an ordinary motor vehicle. The appeal to this Court is based upon the contention that the evidence of Mr. Foster Joy was inadmissible. His evidence was in fact more extensive than the passage referred to by his Honour and it was tendered upon the footing that he was a qualified expert and that the opinions he expressed formed part of the subject of his special knowledge. It is not easy to define the subject of his special knowledge. He said that he was a consulting engineer formerly practising in the city but now at Manly, and he had had fifty years experience of engineering problems in Australia; over a great number of years he had been engaged in investigating road accidents for insurance companies and others and in assessing losses. His investigations covered accidents in which semi-trailers had been involved. He had no engineering diploma or certificate but from 1907 to 1912 he served an apprenticeship with an engineering company and at night studied applied mechanics, drawing, physics and mathematics at a technical college. He described his subsequent employment in various kinds of work related to engineering. The evidence which after objection the witness was permitted to give was not directed to any precise matter of engineering or special knowledge which might have been the subject opinion evidence if Mr. Foster Joy had been qualified as an expert to give such evidence. It dealt with the movements and tendencies of a semi-trailer in an articulated vehicle. The learned judge had ruled that the witness could not state his opinion on the causes of the collision between the two vehicles but under cover of saying as an expert what might cause vehicles to behave in different ways according to circumstances (a thing his Honour ruled that he might do) the witness did in substance and effect put before the jury his opinion in detail of the causes of the accident and how it was brought about. If it had been desired to prove how in fact semi-trailers of the kind driven by the defendant Clark do in practice behave, perhaps a witness or witnesses experienced in their actual use might have given admissible evidence, not of opinion, but of the fact. But Mr. Foster Joy did not possess that experience. If it had been desired to give technical evidence of the physics involved and of any relevant opinions deduced therefrom, possibly that might have been done by a qualified witness although one may doubt how intelligible to the jury the evidence would have been and what useful purpose it would have served. But it certainly does not appear that Mr. Foster Joy was qualified to give such testimony and in fact he did not essay to do so. What in truth occurred was to use the witness to argue the plaintiff's case and present it more vividly and cogently before the jury. (at p491)

4. The rule of evidence relating to the admissibility of expert testimony as it affects the case cannot be put better than it was by J. W. Smith in the notes to Carter v. Boehm, 1 Smith L.C., 7th ed. (1876) p. 577. "On the one hand" that author wrote, "it appears to be admitted that the opinion of witnesses possessing peculiar skill is admissible whenever the subject-matter of inquiry is such that inexperienced persons are unlikely to prove capable of forming a correct judgment upon it without such assistance, in other words, when it so far partakes of the nature of a science as to require a course of previous habit, or study, in order to the attainment of a knowledge of it." Then after the citation of authority the author proceeds: "While on the other hand, it does not seem to be contended that the opinions of witnesses can be received when the inquiry is into a subject-matter the nature of which is not such as to require any peculiar habits or study in order to qualify a man to understand it." Adopted by Harding A.C.J. in Reg. v. Camm (1883) 1 QLJ 136 . (at p491)

5. In R. v. Parker (1912) VLR 152 , one of the cases establishing the evidentiary use of finger prints to prove identity, Cussen J. in that connexion said that expert witnesses may give in evidence statements based on their own experience or study but that they cannot be permitted to attempt to point out to the jury matters which the jury could determine for themselves or to formulate their empirical knowledge as a universal law. To this should be added the observation made by Vaughan Williams J. during the argument of Reg. v. Silverlock (1894) 2 QB 766 , viz. "No one should be allowed to give evidence as an expert unless his profession or course of study gives him more opportunity of judging than other people." (1894) 2 QB, at p 769 The words "profession or course of study" have of course a wide meaning and application; see per Lord Russell C.J. (1894) 2 QB at p 771 . The evidence of Mr. Foster Joy included much that offended against these principles. Some of it was evidence of opinion that lay outside any qualifications that upon any view however benevolent he could be supposed to possess. Some of it was an attempt to guide the jury upon matters which it was within the ordinary capacity of jurors to determine for themselves. Perhaps particular pieces of evidence may be picked out concerning the behaviour of the kind of semi-trailer the defendant Clark drove but Mr. Foster Joy was not qualified by practical experience to give evidence of their behaviour in fact. In short no small part of his evidence was outside the range of opinion evidence by experts and as to more still Mr. Foster Joy was not a qualified expert. The objection to its admissibility should have been sustained. (at p492)

6. This conclusion, of course, means that prima facie the defendant is entitled to a new trial. But a very serious question arises as to whether countervailing considerations exist sufficient to outweigh the prima facie right. After all, the matters about which Mr. Foster Joy spoke were things upon which the jury could judge for themselves unencumbered by his assistance. His evidence really amounted to putting from the witness box the inferences upon which the plaintiff's case rested. A further consideration is that the plaintiff's case is in any case strong and moreover it is now a very long time since the happening of the accident. These considerations are by no means without weight, but on the other side it must be remembered that on the defendant's part the reception of the evidence was strongly objected to, while on the plaintiff's part it was strongly pressed. The purpose was to influence the jury to accept the inferences supporting the plaintiff's case and no one can say that the evidence did not contribute materially to the result. A new trial therefore seems an unavoidable consequence of the inadmissibility of the evidence. (at p492)

7. The appeal should be allowed and a new trial directed. (at p492)

McTIERNAN J. The plaintiff suffered serious and permanent personal injuries in a collision between a panel-van which he was driving on the Pacific Highway towards Gosford and a semi-trailer which the defendant was driving on that road in the opposite direction. The plaintiff alleged in the action that his injuries were caused by the negligence of the defendant, consisting in a breach of his duty to drive the semi-trailer with reasonable care and skill. The defendant denied the allegation of negligence. The case was tried by Maguire J. with a jury, who returned a verdict for the plaintiff with damages amounting to 23,245 pounds. The defendant appealed to the Full Court of New South Wales. (at p493)

2. His major ground of appeal was that the damages were excessive and a minor ground was that a witness, W. F. Joy, a professional engineer, was not sufficiently qualified to give evidence as an expert regarding the movement of a semi-trailer which the witnesses in the case called "jack-knifing". This is a term applied to the behaviour of a semi-trailer by truck drivers when the prime-mover, for example, enters a bend with a downward grade and the wheels of the trailer continuing their course, that part of the vehicle swings away from the prime-mover. (at p493)

3. The Full Court, (Owen, Richardson and Brereton JJ.) unanimously dismissed the appeal. They affirmed the decision of Maguire J. that the witness, W. F. Joy, was sufficiently qualified to give evidence as an expert on the phenomenon of "jack-knifing" and its causes. (at p493)

4. In the defendant's notice of appeal to this Court these two grounds of appeal were taken, but the question of W. F. Joy's qualification to give evidence as an expert was put first and the question whether the damages were excessive relegated to last place. The latter ground of appeal was abandoned at the hearing. (at p493)

5. A witness, A. J. Brown, who was sitting next to the plaintiff in his panel-van, gave evidence of the collision. The plaintiff could not give evidence as to how the accident occurred. He broke down after answering a few questions and could not continue giving evidence. The evidence of the witness A. J. Brown began with events occurring when the panel-van was approaching Piles Creek on the Pacific Highway over which there is a bridge or culvert. The panel-van was travelling north on its correct side of the road. It was descending a grade towards the bridge. The incline on which they were running was about a third of a mile in length. On the opposite side of the bridge the road bent to the right and it was downhill on that road until near the bridge. The witness said that you could see from the panel-van across the gorge between the two sections of the road divided by the bridge, and it was daylight at the time. Continuing his evidence, the witness A. J. Brown said he saw a semi-trailer coming down the road on the further side of the bridge and it was travelling on its correct side when he first saw that vehicle. Then the witness said that he noticed that the semi-trailer "seemed to be going across the road" and that "when it approached the corner I saw the trailer pass the prime-mover of the truck in the centre of the road". He described the movement of the trailer as a "jack-knife". Describing the further movement of the semi-trailer he said its trailer part was coming down on the side of the centre of the road on which the panel-van was being driven, and the trailer part of the defendant's vehicle was passing the cabin of the prime-mover. Before the panel-van reached the bridge the witness said that the plaintiff drove it off the bitumen to the ditch running on their correct side of the road. The evidence shows that this manoeuvre, obviously the only one which the plaintiff could take, did not succeed in taking the panelvan out of the course of the jack-knifing trailer of the defendant's vehicle. The right front end of the trailer crashed into the driver's compartment of the panel-van. The plaintiff suffered most serious injuries and the witness, A. J. Brown, was also injured, but was not rendered unconscious. His estimate of the speed of the semi-trailer when he saw it coming downhill towards the bridge was thirty-five miles an hour and he said that the vehicle did not slacken speed from the time he saw it until the collision occurred. The witness was, according to his evidence, an experienced driver of motor vehicles. At the time the accident happened it was drizzling rain. The evidence of the witness A. J. Brown, which I have set out, states the substance of the plaintiff's case. (at p494)

6. Some particulars of the semi-trailer which appear from the evidence are that it was unladen, its unladen weight was six tons and it was forty-five feet long. (at p494)

7. The defendant gave evidence that there had been enough rain to wet the road, that his semi-trailer was running down the road towards the bridge, its speed was thirty miles an hour and he was driving on his correct side of the road ; and that as he came to the bend in the road he could see the panel-van when it was two hundred yards away. (at p494)

8. The evidence of the defendant, on which he asked the jury to exculpate him from the plaintiff's allegation of negligence, was short. It was to the effect that when he passed over the bridge he "touched" his trailer brakes. He said that is "an extra precaution taken on bends", more so in wet weather ; and when he touched the brakes "the trailer seemed to skid and I slid into a jack-knife and crossed the road". According to his evidence, the trailer was about three feet over the centre line of the road when it collided with the plaintiff's panel-van and pushed it off the road "leaving the corner of the trailer embedded in the side of the panel van". His evidence as to speed "in the very last moment" before striking the panel-van was that the speed "could be probably down to fifteen or twenty miles an hour". The defendant made no allegation of contributory negligence against the plaintiff. The plaintiff's allegation of negligence was founded upon the evidence of the speed at which the defendant drove the semi-trailer down the hill into the bend. The plaintiff sought to prove that speed could be a factor contributing to the jack-knifing of a semi-trailer travelling on a winding road such as that on the Gosford side of the bridge and taking the severe bend in the road. The jury or some of them may not have needed any enlightenment on this subject. But it is not possible to determine a priori the amount of knowledge which a jury may have of the subject or that they have sufficient experience of the behaviour of articulated vehicles to be capable of forming a correct judgment upon it. The plaintiff's advisers acted wisely in calling an expert to give evidence on the subject, especially as the defendant's case was really that his vehicle actually skidded across the road because of its wet condition, thus seeking to negative any negligence on his part. As stated above, the expert was W. F. Joy, a professional engineer. (at p495)

9. In summing up to the jury the learned trial judge gave only the following direction on the expert's evidence. "According to the evidence of Mr. Foster Joy, if you accept it, that sort of vehicle" (an articulated vehicle) "has particular characteristics which are not associated with the ordinary motor car and one of the characteristics, according to his evidence, if you accept it, is on taking a bend an articulated vehicle such as this we are concerned with has a tendency to swing out ; in other words, there is a time lag between the alteration in the direction of the prime-mover on the one hand and the trailer portion of the vehicle on the other". Continuing, the learned judge said this : "You are entitled to consider all the circumstances of the case. What might be a perfectly proper speed to drive any particular vehicle on a straight road might not be a proper speed to drive that same vehicle at, be it semi-trailer or not, when one is negotiating a bend in the road. What might be a perfectly proper speed for any sort of a vehicle on a dry road might not be a proper speed on a wet road. I am mentioning these matters merely as being matters that you are entitled to take into consideration in determining whether or not reasonable care was or was not exercised by the defendant, Mr. Clark, in relation to this particular vehicle on this particular day under the particular circumstances where this accident occurred". In the Full Court, Owen J., who gave the judgment for the Court, dealt with the ground of appeal founded upon the objections to Mr. Joy's evidence at the trial as follows : "In the course of the plaintiff's case, a man named Joy was called, he being a person who is not unknown as a witness in these courts, and who, not infrequently, is called to give so-called scientific evidence in motor-car collision cases. The objection made to his evidence was that it was not shown that he was sufficiently qualified as an expert to give the evidence which he in fact gave. His evidence was to the effect that, where a vehicle such as a semi-trailer is travelling downhill and the prime-mover is turned to its left, centrifugal force tends to cause the rear part of the vehicle to swing out to its right. He said also that where, as here, such a vehicle was travelling at thirty-five miles per hour downhill that tendency would operate, and expressed the opinion that that was probably the cause of the accident. This evidence was objected to on the ground that the witness was not sufficiently qualified to give it. I feel considerable doubt whether it needs such expert knowledge to be qualified to express an opinion of that kind. The matter is one on which I would have thought any intelligent person could speak with some authority but, in any event, I think the witness was sufficiently qualified. He said that he had had considerable experience in the investigation, on behalf of insurance companies and others, of road accidents and their causes, and I think it is impossible to say that the learned judge fell into error in allowing the evidence to be given, although, for my part, I would not have thought that the weight to be attached to it would be very great". This passage contains an accurate statement of the substance of the evidence given by Mr. Joy which the defendant contends was inadmissible. That evidence was clearly admissible if Mr. Joy was sufficiently qualified to give it. At the outset of his evidence he gave some evidence of his qualifications and then he gave considerable evidence without objection. It included this evidence : "Q. You have heard evidence as to the semi-trailer's movement along the road ? A. Yes. Q. With a vehicle such as that, an articulated vehicle, it depends for its movements upon traction from the prime mover, in front ? A. Yes, and in this case it was approaching down a grade - I saw the scene of the accident and I viewed the road approaching the scene, and from the northern end and the southern end, in other words, from the Gosford end and the Sydney end, the road has a bitumen surface approximately twenty to twenty-two feet wide with gravel shoulders eight feet wide on the one side and four feet wide on the other side. They both approach a distance of flat, reasonably level road. They both approach down the grade towards the bridge over Piles Creek and a distance of flat and reasonably level road in two directions - by two directions I mean level longitudinally in the direction of travel and level transversely - there is no bank on the road at that point. Approaching from the Gosford end it is a long grade approximately one in three - I am wrong, one in thirty-three - and it winds slightly but it is approximately - you can see at least a third of a mile of it and it is a downgrade, a gentle well made downgrade all the way. Q. That is from - . A. From the Gosford end coming towards Sydney ; coming from the north and proceeding south. On the other side of the bridge there is also a long wellformed downgrade, slightly steeper, about one in twenty-five and of the same width - twenty to twenty-two feet, of bitumen with gravel shoulders eight feet and four feet. That approaches the level portion at the bottom near the bridge. The two form nearly a right-angle, not quite a right-angle, the junction being the bridge and the flat portion of the highway, thereabouts. Q. The flat portion is south of the bridge ? A. Yes. Visibility for drivers, of both motor vehicles, that is approaching from the southern end or the northern end, would be good. In this case, I was shown a position on the roadway where the Standard Vanguard . . ." That was the plaintiff's panel-van. The objection to the witness giving expert evidence was made when the plaintiff's counsel, having summarized to the witness the material facts proved by the evidence led for the plaintiff describing how the accident happened, asked Mr. Joy this question : "Assuming that happened, what in your opinion was the cause of that occurring ?" In rejecting that question the learned trial judge said that if the witness was sufficiently qualified he could tell the Court what can cause vehicles to move in certain ways, but that is not the same thing as asking him to express an opinion as to what caused the defendant's vehicle to move in the way described in the evidence led for the plaintiff. Then plaintiff's counsel asked a question framed in accordance with the judge's ruling. Counsel for the defendant objected to the question and challenged the qualifications of the witness to express an opinion on "the behaviour of motor vehicles on roadways, and particularly the behaviour of semi-trailers on roadways". Counsel for the plaintiff elicited from the witness that he had investigated accidents in which semi-trailers were involved on a number of occasions, that the accidents had happened on curves and grades and that in cases of some of the accidents a semi-trailer had moved from its side of the road on to the other side and the impact was with the front end of the trailer. The witness further said that over many years he had been considering such problems and had made reports to persons engaging him to consider them. Counsel for the defendant then asked leave of the Court to ask the witness questions on the voir dire. The evidence which the witness gave at the outset before his qualifications were called into question was as follows. He was a professional engineer and had been in practice for thirty-six years and had fifty years experience of engineering problems in Australia and abroad. In the course of his practice he had investigated road accidents for insurance companies and aircraft accidents for Lloyds Aviation Group ; he was Lloyds' aviation surveyor for twenty-five years : during the war he was an engineer officer in the Royal Australian Air Force : he is a past Associate Member of the Institute of Engineers and past Associate of the Institute of Engineer Surveyors. As I have already stated, his evidence proved that he investigated many accidents in which semi-trailers were involved, on curves and grades and where, as in the present case, the surface of the road was bitumen. On the voir dire counsel for the defendant asked the witness questions as to his investigation of accidents in which semi-trailers were involved. The witness gave a number of specific instances. Some were cases in which the witness said that he "personally accompanied the driver on a reconstruction of an accident with regard to the behaviour of semi-trailers attached to prime-movers". Asked whether he had done any automobile engineering course, the witness said he had not, adding that he had been trained in places where automobile engines have been built. His present practice, he said, is particularly "in engineering surveying ; surveying machines" ; and that it also involves "automobile engineering work of various kinds where an opinion is required or an investigation or report with regard to causes of failure or causes of something else happening on roads is concerned, and traffic engineering". In order to carry out such work he said : "You have to have general knowledge of the vehicle and its power, and its weight, its length and its steering, manoeuvring and its braking and the rate at which it travels grade both ways, if there are grades both ways". The semi-trailer in the present case was an "International". In answer to questions the witness said that he had in the course of his practice examined the engines of many of such vehicles and personally inspected and supervised their dismantling and repair. The enquiry into the qualifications of the witness went back to his apprenticeship in the Clyde Engineering Co. at Granville and his studies at the Sydney Technical College where the subjects which he studied were mathematics, applied mechanics, drawing and physics. There is much more in the appeal book which was elicited in the course of the enquiry on the voir dire as to the qualifications of the witness to be called to give evidence as an expert in this case. It is sufficient to say that it strengthens the proofs of his qualifications which have been detailed, if indeed that is necessary. In the case of Reg. v. Silverlock (1894) 2 QB 766 , Lord Russell C.J. discussed the question whether a witness was an expert on handwriting. He said that to be qualified to give evidence as an expert a witness need not become peritus in any definite way. "The question is," said Lord Russell, "is he peritus? Is he skilled? Has he an adequate knowledge? Looking at the matter practically, if a witness is not skilled the judge will tell the jury to disregard his evidence. . . . When once it is determined that the evidence is admissible, the rest is merely a question of its value or weight, and this is entirely a question for the jury, who will attach more or less weight to it according as they believe the witness to be peritus" (1894) 2 QB, at p 771 . In my opinion, there was evidence on which the learned trial judge was justified in holding that Mr. Joy had sufficient knowledge and experience on the subject of the jack-knifing of semi-trailers to warrant the opinion which he expressed as to what are the probable causes of jack-knifing, to be left to the jury, and that the direction which the learned judge gave as to that evidence was correct. I think that the reasons of the Full Court for its judgment on that question are right. In my opinion, the appeal should be dismissed. (at p499)

FULLAGAR J. I agree with the judgments of the Chief Justice and Menzies J., which I have had the advantage of reading, and I do not think that there is anything that I can usefully add. (at p499)

MENZIES J. In an action by the respondent against the appellant for damages for personal injury, the jury returned a verdict in favour of the plaintiff for 23,245 pounds damages. The collision between a panel-van driven by the plaintiff in a northerly direction along the Pacific Highway and an unladen six-ton semi-trailer transport driven by the defendant in a southerly direction, which gave rise to the action, took place at a point on the road some five miles on the Sydney side of Gosford. At the time, light drizzling rain was falling and the road was wet. The plaintiff was unable to remember the accident or anything about it, but the evidence of a passenger in the panel-van, one Brown, was to the effect that the collision occurred because the semi-trailer did not follow the course of the prime-mover as it came up to a left-hand curve on a flat section of the road after coming down a decline, but the front off-side corner of the trailer first projected across the centre of the road, then the trailer overran the prime-mover and both slid or broadsided across the road and crashed into the panel-van, which the plaintiff, attempting to avoid a collision, had swung over to the extreme edge of his correct side of the road. The defendant's version was different. He gave evidence that when he touched his brake, the wheels of the semi-trailer skidded to the right on a mucky section of the road and that the collision occurred when the semi-trailer had reached a line about three feet across the centre line of the road. (at p500)

2. An appeal upon both the question of liability and the quantum of damages was dismissed by the Full Court. This appeal is concerned with the question of liability only, and the one ground taken is that certain evidence tendered on behalf of the plaintiff and objected to on behalf of the defendant was wrongly admitted. The Full Court held that the evidence was admissible. (at p500)

3. The evidence in question was that of Mr. Foster Joy, whom it was sought to qualify as an expert to support Brown's factual evidence by giving scientific reasons for a vehicle behaving as Brown described the movements of the transport. After an examination of Mr. Joy's qualifications as an expert, which, with accompanying argument, covered some twenty pages of the transcript of the proceedings, the learned trial judge ruled in favour of the admissibility of some opinion evidence and said to counsel for the plaintiff: "I have ruled in your favour that Mr. Foster Joy is qualified as an expert, but I do not think it is within the province of an expert witness to express an opinion as to what was the cause of any particular event. He can tell us as an expert what can account for various things, if there are various of them, which can cause vehicles under different circumstances to perform in different ways. That is how it seems to me and that is the ruling I give. I think you had better adhere to it and frame your question in accordance with it." In the course of the evidence that was admitted pursuant to this ruling, Mr. Joy said, inter alia: "A vehicle with or without a semi-trailer attached, particularly with a semi-trailer attached, unladen and travelling down a grade and being suddenly called upon to make a turn, the tendency for the trailed portion of the assembly to swing out due to the turning of the prime-mover, the tendency for the trailed portion of the vehicle to swing out is greater where the speed of the vehicle is increased; in other words, the greater the speed the greater the centrifugal force, the greater the tendency for the trailed vehicle to swing out. It can swing out to such an extent that the prime-mover can endeavour eventually to pull it around into form but it cannot be done quickly. The momentum of the trailed portion which runs into quite a weight at a speed can tend to go on in the direction in which it was primarily travelling and it takes a terrific pull to pull it off its intended direction of travel and there is a lag. Although the prime-mover can clear an obstruction when travelling forward there is a slight lag between the movement of the prime-mover and the movement of the vehicle being trailed. In other words, the primemover can get out of the road of something which can be struck by the front corner of the semi-trailer. . . . It is not uncommon - having seen this scene and noting the grades, the down grade and the flat and the left-hand turn of the grade up, and that turn is as near as - the plan will show, or as near as I can remember - I saw it on Saturday - it is merely at the turn of a right angle turning left. A vehicle travelling down the first grade from Gosford at a speed, not slowly by any means, at a speed and taking the turn, the vehicle gets around the turn and the trailer wants to rush on forward or rush out to the wrong side and that is what I think would happen here." Replying to the following question by Mr. Miller: "I want you to assume that the semi-trailer was travelling at a speed of approximately thirty-five m.p.h. What is your opinion as to that speed in that situation?". Mr. Joy said: "On a left-hand turn? You would expect the semi-trailer to swing out, particularly an unladen trailer." When asked: "In the case of an unladen semi-trailer, is there in your experience, a tendency of the trailed portion to swing on curves?", his reply was: "If you travel sufficiently fast, yes." (at p501)

4. Much of Mr. Joy's evidence was not really opinion evidence at all and it may be that so much as was not inadmissible as irrelevant, but we are here concerned only with that part of his evidence that put forward a scientific explanation for what occurred and was admissible only if Mr. Joy were an expert. As to this, I have, with respect to those who have taken a different view, reached the conclusion that Mr. Foster Joy was not qualified as an expert to express his conjectures, which paraded as scientific opinions, that if the semi-trailer was being driven at thirty-five miles per hour at the place where the collision occurred, it was likely to swing out to its right; or that what happened was that the prime-mover got around the turn and the trailer rushed out to the wrong side - and, therefore, that his evidence to this effect was wrongly admitted. (at p501)

5. Opinion evidence to account for a happening that is described to a witness is admissable only when the happening can be explained by reference to an organized branch of knowledge in which the witness is an expert. As Lord Mansfield said in Folkes v. Chadd (1782) 3 Dougl 157 (99 ER 589) , (as quoted by Lord Merrival in United States Shipping Board v. The Ship St. Albans (1931) AC 632, at p 642 , "the opinion of scientific men upon proven facts may be given by men of science, within their own science". I have no doubt that there is an organized branch of knowledge which would afford an explanation of a semi-trailer keeping on its course as the prime-mover drawing it veered to the left so that in the end the vehicle as a whole crossed to the right of the road, but Mr. Foster Joy was not skilled therein, as his reference to centrifugal force as the explanation of what occurred perhaps demonstrates more forcefully than any criticism of his credentials. It is unnecessary to detail the various qualifications that were relied upon to equip him to express the opinions that he did. It is sufficient to say that such skill as he had was derived from experience rather than from any course of study, and his experience was principally as an engineer concerned with the construction and repair of engines and the construction of buildings. He had also had some experience in the investigation of aircraft accidents and road accidents for insurance companies, and he gave evidence that he had frequently watched the behaviour of semi-trailers. He was not a scientist or mathematician either by study or experience. This is not a case where a witness has some qualifications and it is in question whether they are sufficient to give his opinions the authority of an expert. If such were the case, any appellate court would give great weight to the decision of the trial judge admitting his opinion evidence and would but rarely form an independent opinion of its own upon the sufficiency of those qualifications. This, however, is a case where a review of his evidence reveals that Mr. Foster Joy had no expert qualifications in the branch of knowledge upon which he was allowed to speak as an authority. (at p502)

6. On the question of an appeal court reviewing the decision of a trial judge that a witness is or is not an expert, the statement in Wigmore on Evidence 3rd ed. (1940) vol. II, par. 561, that "the trial Court must be left to determine, absolutely and without review, the fact of possession of the required qualification by a particular witness", if it is intended as a statement of the law rather than of policy - and the words italicized perhaps indicate the latter - is too widely expressed and the American cases cited to support the proposition show that courts of appeal will review the decision of a primary judge upon a witness's qualifications when the qualifying facts relied upon are undisputed, or where there was no evidence of any qualifications, or the primary judge has made a palpable mistake, or his decision "appears on the evidence to be erroneous or to have been founded upon some error of law". See also Nightingale v. Biffen (1925) 8 BWCC 358 ; Wise v. Musolino (1936) SASR 447 ; Enston v. Pardel (1958) 75 WN (NSW) 370 and, further, United States Shipping Board v. The Ship St. Albans (1931) AC 632 ; Shepherd v. Pike (1955) 72 WN (NSW) 85 at p 86 ; Reg v. Spooner (1957) VR 540, at p 541 . In truth, the decision of a trial judge that a witness is qualified to give expert evidence is very much a question of fact and it is entitled to all, but no more than, the weight that a court of appeal gives to a finding of fact upon the hearing of an action. In Bratt v. Western Air Lines (1946) 166 ALR 1061 and the annotation thereto (1946) 166 ALR, at p 1067, what appears to me to be the correct rule is stated as follows: "The qualification and competency of one to give opinion evidence as an expert is primarily in the discretion of the trial court, and the admission or exclusion of such testimony on the ground that the witness was or was not qualified to testify as to his opinion as an expert, will not be reviewed or reversed by the appellate court except where such discretion has been abused, as where there is absolutely no evidence that the witness had the qualifications of an expert and his opinion testimony has been admitted as that of an expert, or where in deciding upon the question of his competency the trial court has proceeded upon erroneous legal standards". (at p503)

7. Evidence having been wrongly admitted, notwithstanding objection to it, the question now is whether this is a case where a new trial should be ordered. (at p503)

8. This is a case where I would have thought that the jury, unassisted by any expert evidence, could on the factual evidence have reached the conclusion that the defendant's transport did first protrude across, and then cross, the centre line of the road because the trailer did not follow the prime-mover in taking the curve, but this circumstance provides no justification for the admission of inadmissible opinion evidence that science explained or supported this version of the happening. It may be that in the circumstances there was no room for the reception of the opinions of experts, because the tendency of a trailer to overrun a prime-mover as it changes course might be thought to be something of which an intelligent but unskilled person would be aware. This is, however, of little importance now because, in my opinion, inadmissible evidence was submitted to the jury, and even if there were no room for expert evidence at all, that cannot now be used to excuse the reception of Mr. Joy's evidence; it is only if the evidence can be regarded as insignificant that a new trial should not follow its wrongful admission. (at p504)

9. The Full Court thought Mr. Joy's evidence to be of little weight, and with that estimate I agree. The plaintiff had a strong case and the defendant, in cross-examination, admitted that he applied his brakes as a precaution to prevent the trailer swinging out. Furthermore, in his summing-up the learned judge, although he referred to Mr. Joy's evidence, did so in terms which emphasized only so much of that evidence as might almost be regarded as a matter of common knowledge. He said: "This was a semi-trailer, as it is called. It was forty-five feet in overall length. Its unladen weight was in excess of six tons and it was an articulated vehicle, and according to the evidence of Mr. Foster Joy, if you accept it, that sort of vehicle has particular characteristics which are not associated with the ordinary motor car, and one of the characteristics, according to his evidence, if you accept it, is on taking a bend an articulated vehicle such as this we are concerned with has a tendency to swing out; in other words, there is a time lag between the alteration in direction of the prime-mover on the one hand and the trailer portion of the vehicle on the other. Gentlemen, if that is the position you might take the view - it is entirely a matter for you as I have said - but you might take the view that the handling of that sort of a vehicle if reasonable care is to be exercised requires some different handling, perhaps a greater degree of care, than would be called for in the matter of driving an ordinary motor vehicle such as you or I might drive". (at p504)

10. These things taken together afford some ground for concluding that notwithstanding that evidence was erroneously admitted, the Court should not exercise its discretion to order a new trial, occasioning, as it probably would, nothing more than further litigation without a different result. This probability is, however, not enough to warrant refusing a new trial. In Piddington v. Bennett & Wood Pty. Ltd. [1940] HCA 2; (1940) 63 CLR 533 , Dixon J. (as he then was) said: "The reception of inadmissible evidence gives an unsuccessful party against whom it was tendered a prima facie right to a new trial. But if it appears that the verdict cannot have been influenced by the inadmissible evidence or that independently of that evidence a verdict other than that found would have been unreasonable or unsustainable the prima facie right to a new trial is displaced". (1940) 63 CLR, at p 554 Here, therefore, the question is whether the verdict cannot have been influenced by the inadmissible evidence, and, having regard to the importance attached to it by both sides, to the fact that it was admitted as evidence of an expert, and to the reference to it in the learned trial judge's summing-up, I do not feel that I can reach an affirmative conclusion on this point. In Balenzuela v. De Gail [1959] HCA 1; (1959) 101 CLR 226 , where the Court decided that a new trial should follow the wrongful rejection of evidence because it could not be said that the evidence rejected could not have affected the verdict, Dixon C.J. said: "When material evidence has been erroneously rejected at the instance of the party who succeeds, then to deny nevertheless to the unsuccessful party the remedy of a new trial the Court must have some sure ground for saying that the reception of the evidence would not have affected the result or that it ought not to have done so". (1959) 101 CLR, at p 232 Later, his Honour said that the true view may be "that at common law it was necessary to grant a new trial unless the court felt some reasonable assurance that the error of law at the trial whether in a misdirection or wrongful admission or rejection of evidence or otherwise was of such a nature that it could not reasonably be supposed to have influenced the result" (1959) 101 CLR, at pp 234, 235 . Although I think it quite likely that the jury would have found a verdict for the plaintiff without the evidence wrongfully admitted, I find that I lack the assurance that Mr. Joy's evidence could not reasonably be supposed to have influenced the result. (at p505)

11. In these circumstances, I think that the appeal should be allowed and that there should be a new trial. (at p505)

WINDEYER J. I have no doubt that, for reasons I shall give, much inadmissible evidence was received. Nevertheless, if it were not that other members of this Court think there must be a new trial, I would hesitate to allow the appeal. Of course a new trial cannot be refused merely because the jury's decision seems to have been right as it seems to me this one was. The issues must be decided by a jury, and by a jury properly instructed and on proper evidence. Yet a new trial may be refused if, disregarding any evidence wrongly admitted, a different verdict from that given would be set aside as unreasonable. And the position here seems to me not far from that. I can see no basis at all for the suggestion that without the inadmissible evidence the plaintiff would not have made a case to go to the jury. The defendant's semi-trailer failed to negotiate a bend in the road and went so far across the road that it collided with the plaintiff's vehicle, although the plaintiff in an endeavour to escape had swerved off on his side of the road as far as he could go. The semi-trailer came to a standstill with the trailer portion across the road and facing west, and with the primemover facing east, its nearside almost touching the nearside of the trailer. These facts alone I think established a strong prima facie case of negligence on the part of the defendant. And a passenger in the plaintiff's vehicle who was called as a witness related what occurred as it appeared to him, using the word "jack-knife" to describe it. This expression has been long used colloquially in the United States, meaning to double-up like a jack-knife. It has apparently been adopted here by drivers of articulated vehicles to describe what happened in this case. It is obvious that when an articulated vehicle, such as a semi-trailer, travelling at any speed, is turned at a sharp corner it may jack-knife, unless it be driven with care. If there be a risk of jack-knifing occurring notwithstanding that the vehicle be driven with care and skill, that would only tend to show that to take such a vehicle on a public road was negligent. And if, as the defendant stated, applying the brakes of the trailer as a necessary precaution against jack-knifing when turning a corner is risky in wet weather because this may cause the trailer to skid, that shows only that the vehicle should be driven at a speed which, having regard to the condition of the road and of the weather, will avoid this risk. The defendant's case was that, without any fault on his part, the trailer skidded on the wet road. It was a matter for the jury; but there was much that told strongly against this. (at p506)

2. It was no doubt necessary for the jury to understand what is meant by a semi-trailer jack-knifing. If it were thought that they would not be aware of the nature of a semi-trailer, a photograph or diagram and a brief explanation by a competent witness of the lengths and weights of the prime-mover and the trailer and the nature of the joint between them, the system of brakes, and so forth, would suffice to enlighten them. Once they were possessed of that knowledge it would hardly be necessary to explain why the equipment might jack-knife on a sharp bend after travelling at a fast speed downhill. If further evidence was thought to be needed of the behaviour on a turn of a semi-trailer, it could be given by anyone with practical experience of driving such a vehicle. To explain jack-knifing in terms of physical causation only an elementary knowledge of physics is needed. It could be done, if it were necessary to do it, in simple terms by reference to momentum, acceleration resulting from travelling downhill, and generally in relation to Newton's first law of motion. Evidence concerning the scene of the accident could always be given by anyone who had seen the place and who could describe what he had seen. Evidence of the width of the road could be given by anyone who could use a measuring tape and had measured it. If evidence were needed of the gradient of the road it could be given by any surveyor who had ascertained it. But the plaintiff's advisers were not prepared to rely on ordinary witnesses to speak of ordinary things. They called one William Foster Joy, thinking apparently that by describing him as an "expert" they could enlist him as an advocate. From the time he entered the witness box the proceedings took a strange course, despite the attempts of the learned trial judge to direct them. The witness described himself as a consulting engineer and a past associate member of the Institute of Engineers and past associate member of the Institute of Engineer Surveyors. What were the particular attainments by which he qualified as an associate member of those bodies, and why he had relinquished his membership did not appear. But at that stage no one seemed really concerned with his competence as an engineer. He was put forward as an expert in the investigation of road accidents] He said he had seen the place where this accident occurred, and he then explained in general terms, and by reference to photographs, the character and gradient of the road. There could be no objection to that, although the police constable or a surveyor who had made a plan could have done it as well or better. But counsel for the plaintiff apparently regarded a road accident as like a bodily ailment, and thought of the witness as if he were a medical expert skilled in the diagnosis of disease who, although he had not seen the patient, might be invited to assume the existence of symptoms described and then asked to give his opinion as to the nature of the ailment. Here was a witness skilled, it was said, in the diagnosis of the causes of road accidents. So counsel related to him what purported to be the circumstances of this accident, and then asked: "Assuming that happened, what, in your opinion, was the cause of that occurring?" Naturally this question was objected to and rejected, the learned trial judge remarking, however, that "if he is sufficiently qualified he can describe the vehicles and how they move and what the result of certain actions is - if he is qualified". His Honour's advice was, however, either misunderstood or unheeded by counsel, for the witness was then asked whether in his "years of experience in investigating accidents" he had investigated accidents in which semi-trailers were involved. He said that he had and that he had reported to the persons engaging him - that was to say insurance companies - and had expressed opinions as to the causes. But telling underwriters what, in his opinion, were the causes of other accidents could not entitle him to tell a jury what he thought was the cause of this one. That should have been obvious. Apparently it was not, for counsel, relying on the additional information he had elicited that past activities of the witness had made him aware of accidents involving semi-trailers, repeated the rejected question. It was still patently inadmissible. But counsel who appeared for the defendant at the trial, instead of objecting, sought and was given leave to question the witness on the voir dire. He cross-examined him about the circumstances of other accidents that he had investigated in which semi-trailers were involved. Forth both sides the question seems somehow to have become, was the witness - an experienced investigator of accidents generally - sufficiently experienced in semi-trailer accidents] After asking some thirty-six or more questions about the circumstances of two or three other accidents to semi-trailers of which the witness had some knowledge, counsel for the defendant submitted that he was not qualified to express an opinion, because, he said, those accidents were "nowhere near the circumstances of this case". Near or far, this was wide of the mark. The witness was an experienced loss assessor and experienced in making investigations for insurance companies into accidents of motor vehicles and aircraft. And if loss assessing and accident investigating involve techniques that are an organized branch of knowledge, his opinion of how losses should be assessed and accidents investigated might perhaps be admissible in an action against a loss assessor or accident investigator for negligently performing his duties. But how could his hearsay knowledge of other accidents, however like this one, make his opinions relevant in this action? His Honour, trying again to bring the matter to somewhere near where it should have been, said: "I would have thought somebody might have asked him what sort of technical knowledge or training is required to understand these things and then asked him what sort of technical training and knowledge he has had". So counsel then turned his attention to this and asked him about his knowledge of automobile engineering. He had no academic qualifications by degree or diploma; but he gave evidence of having served an apprenticeship to an engineering company and having over many years worked for various employers engaged in a variety of engineering undertakings and of having studied, for some period not stated, at the Sydney Technical College. His actual work for most of his employers was he said that of a designing engineer. He had practised as a consulting engineer. In answer to his Honour, he said that he was acquainted with the make of semi-trailer which the defendant was driving. His Honour then ruled that he was qualified as an expert to give evidence within limits, observing that "there is a difference between asking a properly-qualified expert to tell us what can cause a vehicle to behave in a certain way and, on the other hand, asking him to express an opinion as to the cause of this accident". In my view his Honour was, as the matter then stood, justified in accepting the witness as qualified to give evidence of the kind he indicated. He had given an impressive recital of what seemed to have been responsible employments with a number of well-known engineering firms. And, although he was not searchingly questioned on what duties he had actually performed in those employments, it seemed that by his experience and practical training he was qualified to give evidence of fact within the limited area his Honour said he would permit. His Honour was not to know that what he would say, in so far as it went beyond argumentative statements of the obvious, would reveal him as apparently confused on simple scientific matters or as incapable of explaining clearly what he had in mind. He said that on a left-hand turn "you would expect the semi-trailer to swing out, particularly an unladen trailer . . . to radially swing to the right". He was asked what would cause that to happen. His answer was "Centrifugal force of the whole assembly on the turn moving at a speed sufficient for the force behind it to take that weight out". There was a lot more like that; for example he said that "travelling as an unladen vehicle, the road adhesion between the prime-mover and the semi-trailer is less than the road adhesion when there is a lot of weight in the semi-trailer". The plaintiff's case was not that the rear of the trailer swung out, but that the composite vehicle jack-knifed. The witness's evidence was garbled and in parts somewhat contradictory. A new trial cannot be granted because a witness seemingly qualified as an expert shows by his answers much less knowledge than his seeming qualifications suggested or than he professed to have. But what happened here was that inadmissible evidence got to the jury. The witness persistently referred to the circumstances of this accident. He expressed opinions. His evidence thus travelled outside the boundaries that his Honour had properly laid down; and counsel seemingly did not try to keep it within them. The acrid remarks in Taylor on Evidence concerning expert witnesses do not lose significance when the expertise is spurious: "These witnesses are usually required to speak, not to facts, but to opinions; and when this is the case, it is often quite surprising to see with what facility, and to what an extent, their views can be made to correspond with the wishes or the interests of the parties who call them". (at p510)

3. With regret, I agree that, notwithstanding the strength of the plaintiff's case and the failure of the defendant's counsel to persist in his objections, there should be a new trial. (at p510)

ORDER

Appeal allowed with costs.

Order of the Supreme Court of New South Wales discharged. In lieu thereof order that the appeal to that Court be allowed with costs, the verdict of the jury set aside and a new trial be had: the costs of the former trial to abide the event.