Case Profile- Physical Match

As Firearms Examiners, we often are asked to conduct examinations that involve other forms of comparative analysis.  One such request involves what we refer to as Physical Match Analysis.  This type of analysis often involves trying to match two items, from different sources, as having at one time been joined together.  The analysis involves the comparison of fracture contours of both a visual and microscopic nature.

One such case that I recently worked involved the theft of a car, and the suspected switching of parts from the victim's car to the car of another individual.  As you can see in the image below, the victim's car had been stripped of its front end and front passenger door.

A suspect's car was located that had parts thought to have come from the victim's car.

During my inspection of the victim's car I noted a damaged area of body filler at the hinge point of the missing passenger door.  It appeared that some of the filler had been torn away from the car when the door was removed.  This can be seen in the image below.

The front passenger door on the suspect's car was removed for inspection. Noted on the hinge was a deposit of material similar to the material noted on the victim's car.  See below.

Using a rubber casting material (the same material a dentist uses to make casts of teeth) I made casts of both areas so that they could be taken back to the lab for analysis.

Because the casts were a negative impression of the originals, once I got back to the lab I made casts of the casts.  This produced a "positive" or "replica" of the original contours of the suspect fracture points.  The replicas of the originals were fitted against each other in the way the door hinge may have at one time been attached to the victim's car. The resulting irregular fracture characteristics resulted in the physical match seen below.

In addition to the above fracture match, the interior surface characteristics were microscopically compared to each other resulting in these additional positive points of comparison.

Cast from door hinge (left) compared to the cast from victim's car (right).

Cast from door hinge (left) compared to cast from victim's car (right).

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