Interpretation, Collection and Preservation of Glass Fragments

Analysis of the fragments show that the fragments collected from the driver’s side floor included windshield glass and ophthalmic glass. The ophthalmic glass was of the same prescription strength as the first man’s glasses. The police now know who was driving the vehicle when it crashed.

In a case recounted by Gengre (2002) police analyzed the headlight glass found at the scene of a hit and run. They publicized the make and model of the vehicle based on analysis of the headlight glass found at the scene. Shortly after the public broadcast a man turned himself in as the driver stating he assumed they had a witness because they had a description of his car.

It is extremely important to collect all glass found at a scene. Labeling is equally important. Each sample must be labeled accurately with the case number, time, date, and name of the person who collected the sample.

How to Collect and Package Evidence

Reference samples
Reference samples of any glass remaining at the crime scene should be collected for purposes of comparison with glass found on a suspect. Reference samples can be collected from the glass remaining at a scene. Approximately 1 square inch of glass from the point of breakage is required (Saferstein. 2004). Reference samples must be placed in containers which will prevent crushing during transport to the laboratory. These samples should be packed in such a way as to prevent movement inside the container which could damage the edges of the fragment. Damage to the edges would prevent the laboratory personnel from matching the sample with other fragments from a suspect.

In cases where broken headlights, tail lights, light bulbs or bottles are found the entire object can be removed and sent to the laboratory. Again, these items should be packaged in such a way as to prevent further breakage.

When dealing fragments or objects which might contain biological evidence, such as blood or saliva, the investigator should insure that the sample is clearly labeled as containing biological evidence. All biological matter must be dry before it is packaged. Fingerprints can also be recovered from glass and samples should be handled using gloves.

All fragments of glass from a scene should be collected if the aim is to determine the angle or point of impact.

The F.B.I recommends that small fragments be packaged in plastic vials such as a film canister. The vials should be packed so that the fragments do not bounce around inside the container. The fragments must not be allowed to rub together.

When fragments are removed from a frame each fragment should be labeled indicating the inside and outside surface. As well the position in the frame from where the sample was taken should be indicated. For instance the label might read ‘top right corner’.

Small fragments can be damaged by tweezers during collection. Tape may be an alternate method when the pieces are very small.

Finally, all clothing and footwear should be placed in a paper bag, sealed and labeled. Precautions should be taken to ensure the bag is not torn causing the loss of some of the evidence.

 Copyright Info