Tools of the Trade: Dealing with Unusual Surfaces

For the past several years, I’ve taught a class on developing and lifting prints off unusual surfaces. This class is very popular because it shows Crime Scene Officers that the only “surfaces” where you can’t get prints are air and water; everything else can be processed with the right products and the right technique. In this issue, I’ll provide an overview of advanced ways to deal with unusual surfaces.

Multi-Textured/Multi-Contoured Surfaces
Some of the most challenging surfaces to work with are multi-textured or multi-contoured. If you find evidence on one of these surfaces, you need to be prepared. Otherwise, you may have to settle for simply photographing the evidence instead of casting impressions and lifting latent prints. Let’s take a look at a the products and techniques that you can use on these kinds of surfaces.

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New material aids investigators in lifting trace evidence

It’s long been known trace evi-dence, which contends that every contact no matter how slight will leave a trace, can help solve a case. This minute evidence is normally left by objects or substances coming into contact with one another, leaving a small sample on the contact surfaces. Today’s investigators rely on many types of trace evidence, but some of the most commonly and successfully used are fingerprints and toolmarks. To successfully use this evidence, an efficient means of collection must be used. A new casting material from Ultronics Inc. incorporates ease of use, eliminates mixing and applies simply. Researchers set out to exam-ine whether this casting material is a reliable, sensible product for forensic investigators by testing its perfor-mance on a variety of surfaces.

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The benefits of using transparent polyvinylsiloxane for recovery of developed fingerprints on challenging surfaces

Every professional working in law enforcement understands the value of good fingerprint evidence in supporting the investigation of a criminal case. It can assist greatly in the development of a suspect who is possibly associated with the incident and ultimately the arrest and conviction of the actual perpetrator. Good fingerprint evidence can often be the difference between two extremes: getting a confession and conviction—or going through a lengthy and sometimes risky trial based on less-definitive evidence such as witness testimony and other circumstantial evidence. Or even worse, no arrest and no case at all.

A print can often look “good” at the crime scene—or on a piece of evidence back at the laboratory prior to processing—but it might turn out to be almost useless by the time it is developed, recovered, and examined by the latentprint examiner.

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Casting a Wide Net: Lifting Fingerprints from Difficult Surfaces

Casting materials are not just for bite and tool mark impressions, but can be used to obtain fingerprint evidence on rough surfaces, human skin, blood prints, and other types of evidence.

Ask any evidence technician or crime scene detective, “What is the best way to collect or preserve bite and tool mark evidence?” The answer would most likely be: use a casting material. Casting materials are great for recording gouges, scrapes, and scratches in metals and some types of wood products.

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