A.D. Tupper & Associates Limited

For an engineer to produce an analysis, which can be assigned a high degree of confidence, it must be based upon competent data. This means that it is necessary to have full and accurate information about the scene and the vehicles.

The best data derive from direct examination and measurement before the configuration of the scene and vehicles have changed. The location of debris and faint collision marks are fragile, and quickly disappear from the site. Ignoring such information can sometimes affect the confidence level of the analysis. The important point to consider, therefore, is timely collection of scene data.

Often it is not practical or possible for all the data to be collected at the casualty scene. In such cases, a full set of photographs should be taken to preserve the subtle data.

The next best source of information is a timely direct examination and measurement of the site, which is the scene after it as been cleaned up and the vehicles removed. If done within a day or two, most of the surface indicia are still there, or positions can be obtained by interviewing witnesses on site. In this case comparison of scene photographs will prove to be useful.

Often reconstruction cases come to the forensic engineer years after the event, as the case is winding its way through the court system. In some of these cases, a detailed site inspection will reveal gouges that could serve to locate the point of impact, particularly when there are some scene photographs and measurements available.

Even in these old cases, however, as unbelievable as it sounds, I have often found that the subject vehicles are tucked away in a junkyard with the damaged areas undisturbed. They will produce meaningful data upon measurement.

In other cases, where the site has been repaved or otherwise altered, and the vehicles repaired or destroyed, there are no meaningful physical data, and the reconstruction analysis must be based upon photographic information. If the photographs show the relevant areas of the scene and the vehicles, and the analyst is skilled at photographic interpretation and photogrammetry, it is still possible to produce a reconstruction analysis with meaningful results.

The preceding litany gives an outline of some of the sources of data, in decreasing level of desirability, which a forensic engineer can apply to the reconstruction analysis. The point I wish to make in this regard, is that the earlier the expert can be retained and can examine the site and the damaged vehicles, the better will be the reconstruction. It will probably be cheaper, too.

Because of the importance of good underlying data, counsel might well consider retaining the expert to collect and preserve the available data, and hold off on doing the analysis until the disposition of the case demands it.