Friday, July 29, 2016

Forensic Friday: The Mystery of DNA

Alec Jeffreys
It has been thirty years since the first use of DNA to aid in a criminal investigation. Over in the U.K. in 1984, Professor Alec Jeffreys and his colleagues developed “genetic fingerprinting” which uses DNA to identify individuals. Two years later DNA evidence determined the identity of a killer in two related cases of rape and murder. Two years after that, a man serving time for a crime he didn’t commit was exonerated through the use of DNA evidence.

Today’s television shows such as CSI, NCIS, and Law and Order use forensics and witty repartee to find their culprit in less than an hour. In reality, law enforcement officers need much more time to solve their cases. At any crime scene, evidence is painstakingly collected. And I do mean painstakingly-tweezers are often a CSI Technician’s tool of choice. The evidence is then processed through the system (identified, inventoried, and logged). But in order for evidence to be of any use, the detectives on the case must have a working theory. Otherwise the items are simply a collection of artifacts.

So what is DNA? Deoxyribonucleic acid is a self-replicating material that carries the genetic instructions used in growth, development, functioning and reproduction of ALL known living organisms. It is the main constituent of chromosomes. The key in forensics is that DNA is unique for every individual.

During an investigation the detectives must have a reasonable theory with regard to their suspect to be able to request a DNA sample. It is not feasible for the police to request samples of any and every person known to the victim. Therefore, clues and leads must be followed to build a case. Many times non-DNA evidence is sufficient to make an arrest. Other times, DNA is the lynchpin to solve the crime. Unfortunately, law enforcement officers must be patient. According to Forensic Scientist Heather Sergeant on Public Agency Training Council, it takes over fifty four hours to correctly process DNA evidence. Certainly quite a bit longer than our TV characters would have us believe.

What is your favorite TV crime show?


  1. NCIS. I'm very interested to see it this fall without DiNozzo. I don't think I'll miss him!
    I had my DNA tested with No big surprises.

  2. It will be interesting to see the new dynamics without DiNozzo. My dad had his DNA tested to see if he was related to a man with our last name who lived on the west coast. There was no relation which I found fascinating because of the low % of folks in America with our name. I would have thought we'd all be related somehow.