Tire impressions in forensic analysis and identification

Forensic and DNA (Tire Impression)

Tire impressions

Sometimes we fail to be conscious that every movement we make whether in a vehicle or on foot definitely leaves behind some kind of impression. Like the screeching off in a gateway car leaves tire tread marks. The tire impressions left can be subjected to forensic to determine the type of car which entered the place of crime.

Generally impression evidence will occur when a material or object takes on the form of another object especially in terms of direct physical contact. In a trial jury or a judge can consider any type of impression to act as evidence. Upon collection of the evidence by investigators then these impressions are used to find legitimate matches.

Tire impression can be left on within sand, snow, dirt, or mud sometimes on a victim where there is a crime scene. Such tire impressions are majorly collected by casting, photographing, or using the victim's clothes. Even though tire impressions are a bit easier to identify they work the same way footprints works. Using tire impression an investigator can identify the used brand of tire and a further inspection can reveal the defects and wear on a tire treads that was probably caused by gravel, nails, patches, as well as alignment problems capable of identifying a unique set of tires, (Fuller, John., 2008).

There are two types of impressions that can be left at a place of crime. A visible impressions and a latent impression. Visible impression happens when the marks is transferred from a tire to the surface and can be seen by use of our naked eyes without using additional help, for instance tracks left behind by muddy tires on a driveway. On the other hand a latent impression takes when the marks can not be seen by naked eye. Such type is as a result of static charges between the tire and the surface. For them to be seen the investigators have to use chemicals, powders, or alternative light sources. The tire track can be found from road sidewalks, driveways, or any other surfaces.

There are many techniques that can be used in collecting the tire tracks based on the kind of impression that is at the place. Casting techniques is commonly applied when the impressions are within snow, soil, or any other soft surfaces. Casting in tire impression uses a powdered stone material like dental stone, which together with water can be mixed after which poured into the existing impression. Upon drying the method leaves a three-dimensional model of the impression.

In order for the collected evidence to maintain the integrity of the evidence tire tracks has to be properly documented, collected, as well as preserved. Due to the fact that impression evidence can be damaged easily, there has to be steps taken to prevent damage to the evidence. It may involve securing and documenting the place of crime before any collection of evidence, (McDonald, P., 1993). In many occasion general photographs that have been taken from the scene in relation to the other taken scene, in addition to high resolution images of an individual impression.

It is important to have properly photographing impressions. Always impression evidence is collected and presented to the laboratory for it to undergo examination. Where it may be tricky to collect impression evidence then there are different lifting techniques will be used in recovering the evidence, (Bureau of Criminal Apprehension, 2014). They include:

Gelatin lifter: Which is a sheet of rubber that has a low-adhesive gelatin layer on one side capable of lifting prints found in various surfaces such as rough, porous, textured and curved surfaces. Usually it is less tacky as well as more flexible as compared to adhesive lifter, making it capable of picking up the impression without causing tear to the surface.

Adhesive lifter: It is a heavy coating of adhesive that is capable of lifting the impression from smooth, non-delicate surfaces. In several occasion it is used in conjunction with fingerprint powder.

Electrostatic dust-print lifting device: This is a tool that electrostatically works by charging particles found in light soil, which afterwards attracted and bonded to a lifting film. However, it works best when collecting dusty or dry residue impressions on about all the surfaces.

Tire impressions may undergo further enhancement to bring additional minute details. A good example is a digital enhancement program one of them Adobe Photoshop® used in improving the quality of a photographed tire track. Through chemical stains and fingerprint powders investigators are capable of enhancing color of the image or magnify the contrast against the background. As a result the casted or lifted it paves way for scanning or photographing the evidence.

The work does not end at the place of crime but must pass the laboratory where the tires are presented together with the collected evidence. By use of the presented tires examiners makes test standards, impressions of a known source, afterwards undergo comparison with the collected evidence. The process is generally done by use of side-by-side comparisons or transparency overlays.