Crime scene protective gear

DEFINITION: Clothing worn by forensic scientists at crime scenes to minimize their direct contact with materials at the scenes.

SIGNIFICANCE: It is important that forensic scientists, as well as other professionals who attend crime scenes, take precautions to prevent the inadvertent transfer of potential evidence between them and the scenes. These precautions include the wearing of protective gear, which serves both to protect crime scenes from contamination and to protect forensic scientists from coming into direct contact with possibly dangerous substances.

The examination of a is essentially like the examination of any exhibit in a forensic laboratory, in that a main function of the crime scene examiner is to collect from the scene, just as a laboratory scientist collects evidence from an exhibit. Both types of investigators should wear protective clothing during their respective examinations.

The wearing of protective gear at a crime scene serves three primary purposes. First, it minimizes the chances that a forensic scientist will leave at the scene or on samples collected, which could result in contamination of the evidence and thus affect the interpretation of any results. Second, it minimizes the chances that a scientist will carry trace evidence from the scene to the laboratory or to other collected samples relating to the case being investigated or to other cases. Third, it helps protect the scientist from any biological, physical, or chemical hazards at the scene, which may or may not be directly related to the case being investigated.

Protecting the Scene

Simply wearing protective clothing is not enough. Forensic scientists must follow established procedures that specify the kinds of protective gear they must wear, when they must wear it, and when they must change it. They must also follow appropriate crime scene management procedures.

Protocols for the use of protective gear need to consider all the types of evidence that forensic scientists can leave at a scene or collect from a scene. Scientists may shed hairs from their heads or facial hairs. They could shed fibers from their clothing. They could leave fingerprints on any items they touch. In walking through the scene, they could leave shoe prints.

Increasingly, forensic scientists have come to realize that (deoxyribonucleic acid) should be regarded as a form of trace evidence, especially given the steadily increasing sensitivity of DNA analysis. A bloodstain or stain is not a fixed deposit of potential DNA evidence. Rather, just as fibers can be shed from an item of clothing, DNA-containing cells can be shed from a biological stain onto other items or stains. Scientists who attend crime scenes need to be aware of this potential for contamination and must dress accordingly.

Scientists also need to be aware that they may shed DNA from themselves to crime scenes and thus contaminate items. By touching an item, a person can transfer skin cells that could give a DNA profile. Coughing, sneezing, or breathing on objects may also transfer cells. The analysis of this sort of DNA sample, often called trace DNA, is an important part of the work of forensic scientists.

Essential Gear

A minimum standard of protective gear for a forensic scientist generally involves gloves, appropriate footwear, and something that covers the scientist’s clothing, such as overalls or a lab coat. Many are moving to the use of disposable overalls, eliminating the need to have overalls laundered. Disposable overalls make it easy for scientists to change their protective outerwear if it becomes stained or contaminated during crime scene examination, or when they must collect evidence from several areas of a crime scene that need to be kept separate or from multiple scenes associated with the same incident. In addition, because such overalls are disposed of according to protocols established for biohazardous waste, their use minimizes potential contamination from the scene to the laboratory.

Gloves are an essential part of crime scene examiners’ gear because no matter how well-intentioned examiners are, they might accidentally touch important surfaces. Generally, disposable gloves made from vinyl or latex are worn. Some scientists wear two pairs of gloves at a time (a practice called double-gloving), especially when the samples collected are likely to be subjected to particularly sensitive DNA analysis techniques.

Forensic scientists have two options for footwear at crime scenes. Some prefer to keep dedicated pairs of scene boots or shoes, which they clean between scenes with 70 percent ethanol or a surface disinfectant such as TriGene. The other option is the use of disposable overshoes. Both approaches minimize the inadvertent transfer of trace or biological evidence from examiners to crime scenes.

Head coverings and face masks provide an extra level of protection at crime scenes. Forensic scientists may cover their heads with the hoods attached to most disposable overalls or with separate disposable caps. If trace DNA analysis is considered as a possible technique in a case, head coverings and masks should be regarded as essential. Low levels of DNA from persons examining the scene could contaminate these sample types if precautions are not taken, and such contamination could render the DNA results difficult or impossible to interpret. Some scientists consider head coverings and face masks to be essential for all scene examinations, whereas others prefer to address the level of protective gear needed based on individual case circumstances, which may change during their examinations.

Health and Safety Issues

At many crime scenes, forensic scientists can expect to encounter biological fluids. The standard protective gear discussed above should help scientists to avoid possible infection, but some may wish to consider additional precautions if particularly heavy dried or wet blood is present.

Some scene types present particular physical and chemical hazards. For example, examiners collecting evidence at clandestine drug laboratories may encounter volatile chemicals, and they may need to protect themselves with body coverings and breathing apparatuses suitable for such exposure. Because they must often must move through unstable debris, investigators protect themselves with heavy footwear and hard hats or helmets.

In testing substances at crime scenes, scientists may need to use reagents that can present health hazards. For example, the reactive dyes used in presumptive testing for blood and semen can be carcinogenic. Also, crime scene examination techniques involving the use of and leuco crystal violet (for the enhancement of bloodstains and bloodied shoe prints or other impressions) require the spraying of scenes with chemicals. In such cases, some kind of breathing apparatus may be needed, particularly if the area being examined is enclosed or not well ventilated. In some situations, scientists may require protective eye gear as well.

Bibliography

"Collecting DNA Evidence at Property Crime Scenes." National Institute of Justice, 7 June 2023, nij.ojp.gov/nij-hosted-online-training-courses/collecting-dna-evidence-at-property-crime-scenes/evidence-collection/equipment. Accessed 14 Aug. 2024.

Elliot, Douglas. “Crime Scene Examination.” In Expert Evidence: Law, Practice, Procedure, and Advocacy, edited by Ian Freckelton and Hugh Selby. 3d ed. Pyrmont, N.S.W.: Lawbook, 2005.

Fisher, Barry A. J. Techniques of Crime Scene Investigation. 7th ed. Boca Raton, Fla.: CRC Press, 2004.

Geberth, Vernon J. Practical Homicide Investigation: Tactics, Procedures, and Forensic Techniques. 4th ed. Boca Raton, Fla.: CRC Press, 2006.

Houck, Max M., and Jay A. Siegel. Fundamentals of Forensic Science. Burlington, Mass.: Elsevier Academic Press, 2006.

Suboch, Gabriele. Real World Crime Scene Investigation: A Step-by-Step Procedure Manual. CRC Press, 2016.eBook Collection (EBSCOhost), search.ebscohost.com/login.aspx?direct=true&db=nlebk&AN=1261134&site=ehost-live. Accessed 30 Dec. 2016.