Humans share 99.9% identical to every other human. It is the .1% that makes us easily identifiable and distinctly different from most other humans on the planet. This .1% difference make us molecularly unique and easy to identify when it comes to solving crimes. Like a missing puzzle piece, DNA can be taken from a crime scene in the form of blood, hair, skin, other body fluids, bone or any other piece of our bodies that we unknowingly leave behind. During the course of a police investigation, various suspects are under investigation. These suspects are compelled to provide a DNA sample – usually taken by way of a swab of the inside of their cheek. Scientists can then conclusively eliminate anyone who isn’t a match to the crime scene DNA.
As in many scientific advances, there is an acceptable margin or error. In addition, DNA evidence can be thrown out in court by wily lawyers arguing some of the following flaws: mishandling the chain of evidence – basically, a DNA sample is contaminated sometime between when it is collected and when it is tested, sample contamination – other DNA is mixed into the sample by accident or mishandling of the sample in the lab. Finally, identical twins share the same DNA; so if there is any possibility that the suspect could have an identical twin, that twin needs to be investigated and eliminated separately as a suspect. If a lawyer can use any of these tactics to create reasonable doubt, a jury cannot convict. In fact, DNA evidence can be rendered inadmissible if the circumstances under which it was collected violated the constitutional rights of the suspect.
Despite these minor flaws, DNA profiling has revolutionized the sciences of Forensic Anthropology and Criminology:
In 1986 Richard Buckland was exonerated for the rape and murder of a teen in the UK and DNA evidence was used to convict Colin Pitchfork of the same crime in 1987.
In 1987, Tommie Lee was the first American convicted using DNA evidence.
In 1991, Allan Legere was the first Canadian convicted using DNA evidence.
In 2001, Wayne Butler was the first Australian convicted using DNA evidence.