DNA Evidence DNA as Evidence

DNA Evidence DNA as Evidence Organisms on planet Earth use DNA as their genetic blueprint, and each individual organism, including humans, have a DNA sequence that is unique to that individual. That means even within the same species, which share a high percentage of DNA similarity, each individual still has a unique DNA profile. With the discovery of DNA technology, the science of forensics has incorporated DNA technology into the identification of criminal suspects with increasing regularity.

But how a suspect's DNA is discovered, linked to the crime scene, and used as a means of identification is an important aspect to the use of DNA in forensics. Each individual organism possesses a unique DNA signature that can be used as a means of identification.

By scanning 13 separate DNA regions within the genome, it is possible to "create a DNA profile of that individual (sometimes called a DNA fingerprint)." ("DNA Forensics") DNA fingerprinting was first investigated by Alec Jeffreys, an English scientist who, in 1985, developed a technique to use DNA as a means of performing human identification.

("History of Forensic DNA Analysis") Since this time, the use of DNA as a means of identification has grown exponentially, especially among law enforcement, and there are currently hundreds of laboratories that perform DNA identification for such things as paternity tests or criminal investigations. In the realm of forensics, DNA has been successfully collected and analyzed from such substances as blood or bloodstains, semen, tissues and cells, bones and organs, hairs and hair follicles, as well as urine and saliva.

(Catalin, p.2) These things can be collected from such items as weapons, hats, bandannas, eyeglasses, dirty laundry, used cigarettes, stamps or envelopes, used condoms, bed linens, as well as panties or even the body of a crime victim (as in the case of rape). (Catalin, pp.3-4) it is important that these samples be collected as soon as possible as there is the concern of sample contamination or degradation caused by prolonged exposure.

In the case of blood, for example, liquid blood must be stored with a proper anti-coagulant to maintain the blood's liquidity. For other blood samples, they must be dried (if still wet), then placed separately in their own sealed containers, labeled properly as to when and where the sample was collected, and stored in a proper environment; such as refrigerator or freezer depending on the type of sample.

All samples must be properly collected, using gloves and other tools in order to prevent contamination, as well as properly stored until analysis can be performed. It is vitally important that this chain of evidence be maintained so that the evidence collected from using the samples can then be admissible in a court of law.

This requires those collecting and storing samples not only to use gloves and tools to handle the samples, but also to avoid talking, sneezing, coughing, touching one's own body, as well as making certain samples are air dried before storing, using paper bags or envelopes instead of plastic containers, and to "tape, seal, initial, and date all paper bags or envelopes." (Catalin, p.7) DNA is a useful tool in the identification of suspects involved in criminal cases, but there are some limitations to the use of DNA in forensics.

First of all, forensic DNA use is dependent upon the proper collection, transport, storage, and analysis of samples. While forensic scientists take many precautions to prevent degradation and contamination of samples, sometimes contamination occurs and the DNA evidence is usually found to be inadmissible in court. There is also the problem with how identification is translated into an individual. Most DNA tests cannot, with 100% accuracy, match an individual person to a specific sample.