DNA profiling is a recent discovery that has only been used since the 1980s. DNA fingerprinting was discovered, like many scientific breakthroughs, by accident.
Dr. Alec Jeffreys is a geneticist from the University of Leicester in Great Britain. The original project that led to his discovery that DNA can have similar repeating patterns happened through Dr. Jeffreys performing a study on myoglobin genes in seal meat, then comparing it to humans. He noticed that despite the different species, there were similarities in the genetic patterns. His team developed a radioactive probe that would extract and reveal these patterns onto x-rays as DNA "fingerprints." Through further testing of human DNA, he also discovered that children shared half of the DNA from each parent, which is used for paternity testing. His DNA fingerprinting technique was used for the first time to settle an immigration case, bringing worldwide attention to Jeffrey's work. After this discovery, he found that even with DNA having familiar sharing, the lengths of these sequences were unique to each individual and each pattern cannot exist anywhere else in the world except for identical twins.
In a small village of Leicestershire, not far from where Jeffreys was doing his studies, occurred a double rape and murder in 1983 and 1986. Both victims were 15-year old young women. A Mr. Richard Buckland confessed to the second crime, but detectives felt that the details did not match up to the timeline of both murders: Buckland would have been 14 years old at the time of the first occurrence. Aware of Professor Jeffreys' discoveries on identifying individuals through DNA, law enforcement went to him to seek help on these cases. Jeffrey took them on but was not fully confident that he would be able to crack it: no one had ever done a DNA analysis for a crime scene before. Despite his concerns, his testing confirmed that the DNA blood and semen samples found on both victims matched, thus both were raped and murdered by the same person. Following those results, through comparative testing of the blood and semen of Buckland to the fluids found at the second murder, Jeffreys' DNA fingerprint technique revealed that the blood and semen from the murders did not match Buckland. This would be the first case of DNA testing exonerating a person from conviction.
Once it was established that Buckland was innocent and that DNA fingerprinting can be successful, came the challenge of identifying the murderer. Police launched village-wide testing of all 5,000 men. Once they were narrowed by matches to the blood type found at the crime scenes, their semen was tested. Despite the DNA profiling successfully clearing Buckland, none of the samples from the village matched. The public and police were disappointed and concerned about the whereabouts of the killer.
For a year, Colin Pitchfork, resident baker, avoided having his blood tested. He swapped his passport photo with a colleague Ian Kelly, which police were using as identification in the massive search, to have Kelly's blood tested instead of his. A woman in the village went to the police after she overheard a man claiming to have given his blood on behalf of Colin Pitchfork. Pitchfork was arrested and had his blood tested, revealing a match to the crimes. Colin Pitchfork was convicted to a life sentence for both murders. This case was the first in history to use DNA profiling to free the innocent and solve crimes.
DNA Profiling revolutionized forensics and the criminal justice system. Thanks to this discovery and further discoveries in DNA forensics, countless convictions were overturned with DNA testing, giving the innocent the concrete evidence to go free. It also ensured that the accused were properly convicted for their actions.
US National Library of Medicine & National Institute of Health: Discovery, development, and current applications of DNA identity testing
BBC Newsnight: DNA pioneer's 'eureka' moment
DNA Forensics News: DNA Fingerprinting