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Collection and Analysis of Evidence - Dna

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Final Project

Lauren Hawley

Thomas Edison State College

        The collection and analysis of DNA evidence is a technique used in helping to determine the person responsible for violent crimes or assaults and it is also used for ruling out suspects.  This technique requires that the crime scene and the victim to be searched and examined for evidence that may contain DNA samples of the perpetrator.  Evidence can be found anywhere and “The best evidence occurs when a person’s DNA is found where it is not supposed to be.”  ( A Simplified Guide To DNA Evidence , 2013)  The following list from the National Institute of Justice is only a partial list of where DNA can be found and the possible source of DNA:


Possible Location of DNA on the Evidence

Source of DNA

baseball bat or similar weapon

handle, end

sweat, skin, blood, tissue

hat, bandanna, or mask


sweat, hair, dandruff


nose or ear pieces, lens

sweat, skin

facial tissue, cotton swab

surface area

mucus, blood, sweat, semen, ear wax

dirty laundry

surface area

blood, sweat, semen




used cigarette

cigarette butt


stamp or envelope

licked area


tape or ligature

inside/outside surface

skin, sweat

bottle, can, or glass

sides, mouthpiece

saliva, sweat

used condom

inside/outside surface

semen, vaginal or rectal cells

blanket, pillow, sheet

surface area

sweat, hair, semen, urine, saliva

"through and through" bullet

outside surface

blood, tissue

bite mark

person's skin or clothing


fingernail, partial fingernail


blood, sweat, tissue

(DNA Evidence: Basics of Identifying, Gathering and Transporting, 2012)

When looking for DNA on an assault or rape victim, the areas to be searched are located on the victim’s body.  “Evidence on or inside a victim’s body should be collected by a physician or sexual assault nurse examiner. A medical examination should be conducted immediately after the assault to treat any injuries, test for sexually transmitted diseases, and collect forensic evidence, such as fingernail scrapings and hair. Typically, the vaginal cavity, mouth, anus, or other parts of the body that may have come into contact with the assailant are examined.” (Understanding DNA Evidence: A Guide for Victim Service Providers)  

The DNA samples must be handled with care so that the DNA and evidence will not be compromised nor degraded.  DNA can degrade when it is exposed to heat or humidity so the sample must be stored in a cool place.  Once a sample is dried, it can stay at room temperature if the humidity is controlled.  However, liquid samples must be transported and stored in refrigerated or insulated containers. ( A Simplified Guide To DNA Evidence , 2013)  

        The topic of using DNA as evidence is particularly interesting to me because I am, and always have been, interested in biology and using DNA to catch criminals is fascinating to me.  The idea that such identifying information can be obtained from such a microscopic piece of physical evidence is amazing and seems almost magical.  DNA is the building blocks of life and is “the genetic material that organisms inherit from their parents” (Reece, Urry, Cain, Wasserman, Minorsky, & Jackson, 2011) and “with the exception of identical twins, no two people have the same DNA.”  (Understanding DNA Evidence: A Guide for Victim Service Providers)  A small sample of DNA that is barely usable can be elongated to make it a sample that much information can obtained from.

        It has not been that long that DNA has been used as evidence in a court of law.  DNA was first used as evidence in England in 1986. DNA samples were collected from men living and working in the neighborhood of two rape and murder crime scenes and resulted in two positive outcomes. The man originally convicted was proved to be innocent and the guilty criminal was caught. A year later, DNA was first used in a United States criminal case in that occurred in Florida. The forensic evidence that was collected from a rape victim was positively matched to a suspect’s DNA and when presented in court, the suspect was found guilty of the crime. (Hirby)  DNA being used as evidence is now so commonplace that there is a “toy DNA lab based on the CSI TV series is available at”.  (James, 2009)



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