truck. It was daylight, the weather clear and the roads dry.
There were no eyewitnesses to the accident. Both drivers were alone, and the truck driver was neither deposed nor called to testify at trial. One of plaintiff's witnesses, a postman, testified that although he was between 200 and 300 feet from the intersection when he heard the collision, he did not see it happen.
There were no skid marks by either vehicle at the scene of the accident. Photographs taken at the accident site by the police do not reveal the presence of skid marks and none were observed by witnesses.
It is undisputed that the motorcycle struck the truck's right rear wheel in the southeast corner of the intersection. Photographs of the debris at the scene and the testimony of the postman establish this as the general area of the collision. A more precise location cannot be established in view of the fact that the motorcyclist did not survive the accident, the truck driver was neither deposed nor called to testify, and the deposition of the investigating officer was not offered into evidence. The postman testified that after hearing the crash he proceeded towards the intersection to investigate. He observed that part of the truck had already cleared the intersection and was at rest in the eastern portion of Tennyson Street. He saw the motorcycle lying against the south curb, five feet east of the eastern curb line of Tennyson, the body of the decedent positioned near it, and his helmet 90 to 100 feet into the eastern portion of Tennyson Street. The postman also testified that he watched the truck driver stand the motorcycle up and turn it around and then saw him drive his truck out of the intersection and park it 150 feet further east on Tennyson. The driver then returned to the accident site and began mopping up the oil spill from the motorcycle.
Since both vehicles were moved before the police arrived, the photographs taken at the scene of the accident do not indicate the position of the vehicles immediately after impact. Although the photographs were received into evidence, they merely depict various views of the intersection and show the damage to the two vehicles. There are no photographs of the position of the decedent's body since he too had been removed from the scene when the police arrived.
The measurements taken at the scene of the accident by the investigating officer were not offered into evidence. However, it should be noted that the only measurements which he took were the width of the two streets and the estimated point of collision. As indicated above, there were no skid marks to measure and the two vehicles had already been moved from the point of impact before the police arrived.
Plaintiff presented no evidence of the condition of the brakes of either the truck or the motorcycle. Nor was any evidence introduced concerning the kind, condition or inflation of the tires of either vehicle. There was no testimony as to the type of street surface at the accident scene.
Aside from the testimony of the postman, who did not witness the accident, and a neighbor, who also testified as to the position of the decedent's body after the accident, plaintiff's entire case as to defendant's liability rests exclusively upon the testimony of the expert witness.
Plaintiff called as an expert witness on accident reconstruction a scientist and engineer specializing in mechanical engineering and related physical sciences dealing with automotive work. He testified that 17 months after the accident he visited the intersection of Tennyson and 33rd Streets where the accident occurred. There he took various sight-distance measurements. He then visited the Colonial Fuel Company where he inspected the truck which had been involved in the accident. No evidence was received concerning the use of the truck over the 17-month period. From these visits and inspections almost a year and a half after the accident, and primarily from a detailed examination of the photographs received into evidence, the expert attempted to reconstruct the speed of both vehicles and to explain how the collision occurred.
Although acknowledging the absence of skid marks in any of the photographs, he claimed he was able to discern "brake marks" in one of the photographs which he "assumed" came from the truck involved in this accident. He testified that his measurements of these brake marks in this one photograph enabled him to deduce the speed of both vehicles and conclude that the truck had failed to stop for the stop sign before proceeding into the intersection. He testified that the brake marks, when read in conjunction with such factors as the damage to the two vehicles and the location of the body, helmet, cycle and oil stains, enabled him to employ the laws of dynamics and physics to reconstruct the accident. It was his expert opinion that the truck proceeded through the stop sign at 23 miles per hour and braked to 13 miles per hour when the motorcycle travelling 25 miles per hour collided with it.
Therefore, the issue before this Court was to determine whether the factual foundation for the expert's opinion testimony was so conjectural and speculative as to constitute error to permit the jury to consider the credibility of such opinion on the issue of liability.
Since expert opinion testimony constitutes an exception to the general rule that opinion testimony is inadmissible, its admission should be limited within the bounds of necessity. It is for this reason that the qualification of an expert witness and the limitations imposed on his testimony are left to the sound discretion of the trial judge. Salem v. United States Lines, 370 U.S. 31, 35, 82 S. Ct. 1119, 8 L. Ed. 2d 313 (1962); Reagan v. Sinclair Refining Co., 319 F.2d 363 (5th Cir. 1963), cert. denied, 376 U.S. 956, 84 S. Ct. 975, 11 L. Ed. 2d 974 (1964); Harvey's Inc., v. A.C. Electric Co., 207 A.2d 660 (D.C.App.1965). As the Supreme Court said in Salem, "the trial judge has broad discretion in the matter of the admission or exclusion of expert evidence, and his action is to be sustained unless manifestly erroneous." 370 U.S. at 35, 82 S. Ct. at 1122, 8 L. Ed. 2d at 317.
Four conditions must be satisfied before the trial judge, in the exercise of his discretion, may decide as a matter of law that expert opinion testimony may be received at trial. First, the trial judge must be satisfied that the expert has the necessary expertise in the specific area about which he expresses an opinion. This may result from his education, training or experience in his field. Second, the area of inquiry should require an employment of the principles of science, engineering, business or other occupation beyond the ken of the average juror. Third, and crucial to this case, the expert's opinion cannot be based on speculation or conjecture, but must be grounded on evidentiary facts in the record or reasonable inferences arising therefrom. And finally, there must be an apparent need for such expert testimony in order to aid the jury in their resolution of the issue.
The sine qua non of expert opinion testimony is that its basis be grounded in fact -- not conjecture. As such, the opinion testimony of an expert witness may either be based upon facts within his own knowledge or upon hypothetical questions which assume a state of facts supported by the evidence. In either case, however, the opinion of the expert witness must be based upon proved or assumed facts which are sufficient to form a basis for his opinion. In Atlantic Life Insurance Co. v. Vaughan, 71 F.2d 394 (6th Cir. 1934), cert. denied, 293 U.S. 589, 55 S. Ct. 104, 79 L. Ed. 684 (1934) the court expressed the familiar rule thus:
"While the courts will give wide latitude to the reception of expert opinion evidence, we think it is axiomatic that it must be based upon conceded or proved facts, and that a naked opinion, based obviously on mere speculation and conjecture, does not rise to the dignity of evidence, . . ." 71 F.2d at 395.
Consequently, should the factual foundation of the expert's opinion prove nebulous, such testimony will not be admissible into evidence.
Accident reconstruction hinges primarily on the determination of speed at time of impact. Absent eyewitnesses to the speed of the vehicles prior to collision, other factors must be considered. In general, the factors which play a major role in speed reconstruction and which are most often relied upon by experts are skid marks, vehicle damage, vehicle characteristics, highway conditions, and vehicle position after impact. Consequently, in order to evaluate this expert's opinion testimony regarding the speed of the two vehicles at impact, it is important to focus our attention on two aspects: first, to determine which of these factors comprise the factual foundation of his opinion testimony, and second, to examine the nature of these factors in the context of this accident.
A factor of considerable importance to the present case is the striking absence of skid marks by either vehicle. It is generally recognized that where skid marks and other physical facts are present, a law enforcement officer, accident investigator or safety engineer who qualifies as an expert in accident reconstruction may give opinion testimony as to the speed of the vehicle which made them.
The absence of skid marks, however, seriously discredits the opinion testimony of such an expert. Moreover, if, in addition to the absence of skid marks, the other physical facts surrounding the accident are either unknown or of a highly speculative nature, such expert opinion testimony as to speed must be rejected.
A case which exemplifies this proposition and bears a striking similarity to the situation which confronts this Court is Campbell v. Barlow, 274 Ala. 627, 150 So.2d 359 (1962). Like the present case, the trial judge in Campbell was confronted with an expert witness who sought to give opinion testimony as to the speed of two vehicles where no skid marks were in existence. The court examined the other physical facts surrounding the accident upon which the expert based his estimation of speed. These were the distance the vehicles traveled from the point of impact, damage to the vehicles, the manner in which the debris was scattered, and the markings on the road after impact. The court concluded, in light of the absence of skid marks, that these other factors were not sufficiently probative to permit the expert to give opinion testimony as to the speed of the vehicles. In ruling his testimony inadmissible the court said:
"We are led irresistably to the conclusion, from the absence of any skid marks or other evidence from which a reasonable opinion as to speed could be predicated, that the trial court committed prejudicial error in overruling appellant's well-grounded objection to the testimony." 150 So.2d at 360.
Like Campbell, this Court is confronted with an accident which produced no skid marks and few physical facts of a certain nature. Therefore, in view of the marked absence of skid marks, it is important to focus our attention on the nature of the other physical facts surrounding this accident. However, before doing so, one aspect of plaintiff's evidence on the subject of tire marks merits closer examination.
The expert witness testified that he inspected the photographs taken at the scene of the accident. He acknowledged the absence of skid marks in them. However, in one of the twelve photographs received into evidence, plaintiff's exhibit 2A, he testified that he detected "brake marks." He explained that these were caused by rubber from the tire being implanted on the road surface, but in a manner not as pronounced as skid marks. He testified that from a measurement of these marks in the photograph and a consideration of the other facts of the accident, he was able to calculate the point of impact in order to arrive at the speed of the truck at collision and conclude that it had not stopped for the stop sign.
Although photographic evidence of tire marks may be admitted into evidence, this is always subject to the rule that there must be evidence to connect such marks with the vehicle which allegedly caused them. This rarely presents a problem since the tire marks at the scene of an accident have usually been examined, measured and compared with the vehicle which made them in order to verify their identity. Here, however, the existence of the brake marks seems to have first become evident when the expert examined the photographs 17 months after the accident. The most serious dilemma which this poses is that, although the photographs were received into evidence, no evidence was introduced to link these marks with defendant's truck. It is hard to see at this stage how any such evidence could be introduced. In fact, the most obvious difficulty with the expert's testimony on this point is that he matter of factly assumed that the brake marks which were in the photograph were made by the truck. There was no testimony by any other witness that the brake marks in question were indeed made by the truck which was involved in this accident. The Court examined the expert closely on this matter:
"Q. How can you say that [the brake marks] were from the truck?
A. They are dual tire marks, your Honor. And . . . .