A Brief History of DNA Testing


Since the advent of DNA testing in 1985, biological material has emerged as the most reliable physical evidence at a crime scene, particularly those involving sexual assaults or crimes of violence. DNA, or deoxyribonucleic acid, contains the genetic blueprint that is unique to each person.

Though DNA testing made its first appearance in the context of the criminal justice system in 1980s, it was rudimentary at first. Juries were hesitant to convict based on DNA, given both the novelty and lack of understanding surrounding the evidence. Throughout the late 1980s and 1990s, however, DNA testing became less expensive and far more accurate. In 1987, a Florida rapist became the first individual in the United States to be convicted on the basis of DNA evidence. Two years later, DNA evidence exonerated the first individual – an Illinois man named Gary Dotson, who had served a decade in prison for a rape he did not commit. Though Dotson’s exoneration was not heralded with great fanfare outside his hometown of Chicago, it was the beginning of a new era of accuracy and certainty in revealing and proving claims of wrongful conviction. 

What most research has since revealed is that DNA exonerations represent only the tip of the iceberg. While it can be powerful exculpatory evidence, DNA is only available in a small fraction – between five and ten percent – of criminal cases. Although DNA exonerations make up a smaller percentage of the total number of exonerations, the publicity and public awareness generated from a series of high-profile exonerations – including the exonerations of individuals who had been sentenced to death – has led to greater scrutiny of existing convictions, and a greater willingness to investigate a potential miscarriage of justice. The consequent upsurge in research began, for the first time, to influence best practices in government and law enforcement.