Forensic Science and DNA in Crime Solving

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Cynthia Flores

May 13, 2004

Criminal Law for Criminal Justice: CJ230-02

Larysa Dolyniuk                

Forensic Science and DNA in Crime Solving

Forensic Science is defined as the “application of science to law and the investigation of criminal activity” (Forensic Files). Forensic science is made up of many different areas of expertise that are interrelated and work together to solve even the most baffling of crimes. Forensic scientists are now able to turn even microscopic evidence into strong physical evidence. This allows investigators to solve crimes that were once impossible to solve. That includes crimes with no witnesses, no suspects, no known motives, no visible evidence, and in some cases—no bodies. With the advances of forensic science and DNA testing, comes a stronger understanding and acceptance of its validity by society. Jurors were not so sure about DNA evidence when it was first used in courtrooms, since their knowledge of the subject was limited. Now, it is very seldom that a prosecutor will rely solely on circumstantial evidence when trying a criminal case.

There are many uses for DNA and it has quickly become one of the most widely used forensics tools for investigators. DNA can positively identify human remains, eliminate or exclude a person as a suspect, exonerate innocent people, prove a suspect’s involvement in a crime, and place a suspect at the scene of a crime. In cases that involve blood evidence but missing a body, reverse paternity DNA testing can be done to determine if the blood found belongs to a particular person.

It was in 1984 that Sir Alec Jeffreys developed the first DNA profiling test. DNA (which stands for deoxyribonucleic acid) “is the genetic material found in the body’s nucleic cells (those with a nucleus) such as white blood cells, semen, bone, skin, and hair”(Wells). Aside from the usual blood and semen that can be found at a crime scene and tested, DNA can be found on items that most criminals would never even think of. Cigarette butts, cups, beer bottles, envelopes, lipsticks or chap sticks, and even tissues can be used to obtain a DNA sample.

DNA profiling was first introduced to US criminal court during a rape case in Florida in 1987. Tommy Lee Andrews, a factory worker, was convicted of a series of rapes based on DNA evidence (Wells). In 1989, the first post conviction DNA testing resulted in the exoneration of an innocent man convicted of murder in Virginia. David Vasquez, a borderline retarded man, allegedly confessed and pled guilty to sexually assaulting and murdering a woman in 1984. He later said he had only “dreamed it.” DNA testing later proved that the true killer was Timothy Spencer, a man who was responsible for several other rape-murders. With this DNA test proving his innocence; Vasquez was released in 1989 after serving five years. Although he was not tried for the Vasquez case, Timothy Spencer was convicted of two other rape-murders. He became the first person in the United States to be executed based on DNA testing (Connors).

In 1992, the FBI started a national DNA database. The goal was to get each state to build its own DNA database by obtaining DNA samples from all convicted offenders, feeding them into a database, and linking them together so that DNA found at crime scenes could be matched to known offenders (Willing). Every state now has a database, and all offenders convicted of violent and/or sexual crimes are required to submit to a DNA sample recovery. This allows investigators to obtain a DNA sample from a crime scene and feed it into the database to determine if it matches any known offenders.

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Along with human DNA evidence, DNA markers are also found in plants and animals. When Shirley Duguay was reported missing, police found her car abandoned in a field with blood spattered on the windows. Police searched the area and found a bag that contained a bloody jacket and a pair of men’s shoes. On the jacket, police found white cat hairs. Forensic tests proved that the cat hairs came from the suspect’s cat, Snowball. It was the first time animal DNA testing had ever been done and the first time it was ever used to convict someone of a crime ...

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