How DNA Typing Helps Solve Crimes

The CSI tour Las Vegas introduces you to many criminal forensics tools, including one that has only existed since 1984. Deoxyribonucleic Acid (DNA) testing now has multiple crime databases devoted to it, but its development wasn’t intentional.

DNA Discoveries

DNA testing stemmed from the research of English geneticist Dr. Alec Jeffreys who discovered the uniqueness of each individual’s mini satellite section of a DNA sequence. Jeffreys developed a measurement method so researchers could distinguish the difference in DNA sequence lengths, thus letting them use DNA to perform human identity testing. Combined with Kerry Mullis’ 1983 discovery of the polymerase chain reaction (PCR), it enabled the PCR test.

The Narborough Serial Murders

The testing method quickly became assimilated into criminal investigations. It was first used in 1986 in a massive effort to discover the perpetrator of two murders and sexual assaults of two girls from the English village of Narborough. Lynda Mann and Dawn Ashworth both died in the Leicestershire, England area. The modus operandi (MO) matched in both cases. Police recovered DNA evidence in the form of semen at both crime scenes. Police were able to rule out the man who confessed through DNA testing. The determined police force then collected and tested the DNA of more than 4,000 men in three surrounding villages. The DNA of Colin Pitchfork matched the semen found at both crime scenes. Its use in court led to the conviction of Pitchfork, now serving a life sentence in Wambaugh prison.

The National DNA Index and CODIS

Culling DNA evidence at a crime scene soon became an accepted practice. Today, the National DNA Index houses more the seven million offender profiles plus nearly 269,000 forensic profiles. The 90,900 CODIS matches have helped solve more than 89,600 criminal cases. Visit the Las Vegas CSI exhibit to learn more about forensic evidence techniques.


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