Reference no: EM132286169

150 WORDS AGREE OR DISAGREE

1. Explain the proper collection and packaging methodologies for biological evidence. Why should biological evidence never be packaged in air-tight or non-breathable mediums?

The proper collection and packaging methodologies for biological evidence is important for investigators to follow in order to properly preserve evidence and not allow it to be contaminated. First, to explain what biological evidence is classified as, we will describe a few of the different specimens.

Blood, saliva, or semen are common types of bodily fluids that can be retrieved at a crime scene. In order to properly contain these specimens, investigators will use a cotton swab that is encased in a plastic cover to protect the swab from being contaminated and they label where and when the located the specimen (Plaza, 2016). Fingerprints or teeth marks are other forms of biological evidence.

These can be lifted using adhesives that can pull the print from the piece of evidence. If the adhesive will destroy the evidence, then the investigator will take a photograph of the dusted print and use this to examine in the lab. Teeth marks can be copied using a type of plaster that will fill the cavity left by the bite. This can be compared to dental records (Dorion, 2011).

Storing biological evidence is complicated because if you store it in air-tight container can damage the evidence by allowing it be effected by outside temperatures that can cause bacteria to grow on the evidence if not allowed to breath.

Keeping the material in a dry location with a controlled temperature can preserve the evidence for a longer period of time. Not allowing the evidence to be stored properly can also cause the evidence to dry up and no longer be useful. Once DNA is damaged, it cannot be replicated or repaired (Lee, 2011).

2. What is PCR analysis? Why is this application important particularly for cold cases or cases in which only a small amount of DNA is recovered?

PCR is Polymerase Chain Reaction and is a test that replaced the Restriction Fragment Length Polymorphism test in the late 1990s (Minor, 2013). This test I able to develop a DNA sample and profile from biological evidence that was once deemed extremely small (DOJ, 2002).

This test is able to do so by copying the DNA and reproducing it without causing damage to the original piece of evidence. This process is very important to cold cases because investigators have the ability to reconstruct DNA from evidence that may have previously been deemed damaged. When DNA evidence is damaged or only a small amount remains, this test can help investigators piece together the events and possibly assist in solving the cold case.

3. What is STR analysis? Why is this an effective method for DNA typing?

STR analysis is Short Tandem Repeat technology that can evaluate a specific region of DNA (DOJ, 2002). This test is able to compare DNA samples and identify the matching profile against the other samples. According to the Department of Justice, "the likelihood of two people matching the 13-loci of a DNA sample are greater than 1 Billion to One (DOJ, 2002)."

This test can verify those 13-loci and if a match is not found, they can dismiss that individual as being a suspect. The FBI uses these 13 different loci to use as their database for CODIS (DOJ, 2002).

This core set gives them a greater chance of matching suspects and takes away any doubts of how the sample is tested so they can avoid false alerts. Having an established criteria to follow allows the different regions to be on the same page, and being on the same page as other areas allows for a greater possibility of finding the right suspect.

References:

Department of Justice. (2002). Using DNA to solve cold cases. NIJ Special report.

Dorion, R., & Dorion, R. (2011). Bitemark evidence a color atlas and text (2nd ed.). Boca, FL: CRC Press.

Lee, S., Clabaugh, K., Silva, B., Odigie, K., Coble, M., Loreille, O., Crouse, C. (2011). Assessing a novel room temperature DNA storage medium for forensic biological samples. Forensic Science International: Genetics, 6(1), 31-40.

Minor, J. (2013). Touch DNA: From the crime scene to the crime laboratory. Forensic Magazine.

National Forensic Science Technology Center (2013). A Simplified Guide to DNA Evidence.