How DNA diagnostics began: The Colin Pitchfork murder case

In 1983 and 1986, the British police struggle with two murders. Until geneticist Dr. Alec Jeffreys brought us RFLP. Genetic fingerprinting was born.

The epiphany came early in the morning in the darkroom

At 9am on 10 September. 1984, Dr Jeffreys was working in the darkroom, investigating the evolution of the gene responsible for the oxygen-transporting protein in muscles, myoglobin, and had photographed corresponding sections of DNA for it after gel electrophoresis. Dr. Jeffreys looked at the freshly developed film recording: it showed the DNA in several bands that looked like bar codes on packaging. "My God," he is said to have thought, "what have we got here?" Completely different patterns, and so unique that any human could be identified by them. Just a few hours later, Dr Jeffreys and his colleagues named the chance discovery a "genetic fingerprint".

With this technique, by 1987 DNA from semen traces was isolated to reconstruct the DNA profile of the killer. 5,000 men from 16 to 34 with no alibi were asked to give a blood sample. Of course, the police assumed that the killer would not let himself be examined voluntarily. It also happened rather by chance.

In August 1987, a woman from a bakery told the police that one of her colleagues mentioned that he had given his blood as a substitute for someone else’s to help him. When Ian Kelly was questioned, he did not deny it. It was his buddy, 27-year-old Colin Pitchfork (born 1960), who had made Kelly believe that he had also given his blood for someone else who was in trouble.

The reason: he was the murderer

In January 1988, Pitchfork pleaded guilty and received a long prison sentence. He cannot be released until 2023 at the earliest. Pitchfork was the first murderer in human history to be convicted with his DNA.

By contrast, a mentally disturbed 19-year-old man, Rodney Buckley, had previously pleaded guilty to killing Dawn Ashworth. He was set free because his DNA absolutely did not match the sperm DNA at the crime scene. Buckley was instead the first suspect in human history to be acquitted based on DNA analysis.

DNA tests as evidence

In 1987, DNA tests were officially admitted as evidence for the first time in the USA and England. The UK national DNA database contains about 700,000 DNA profiles and has been used in 75,000 investigations, about 500 times a week. In 10,000 rape cases between 1989 and 1996, 25% of the first suspects could be excluded by DNA analysis.

It has been shown that even eyewitnesses are often mistaken, as noted in the US Justice Department: The Innocence Project, by New York lawyer Barry Scheck calls DNA the "gold scale of innocence" and has been able to get 375 innocent people out of prison through DNA analysis since 1992, including 15 death row inmates. Scheck says that for every 7 people executed in the US, at least one is innocent. Scheck also defended O.J. Simpson. As for Dr. Alec J. Jeffreys, he was knighted  by the British Queen for his services to humanity.

Genetic fingerprints have been used for identification since 1992

Even identical twins have different fingerprints. The case of the US football star O. J. Simpson (born 1947) brought molecular DNA fingerprinting to worldwide media attention. In the end, Simpson could be be convicted for the murder he was accused of. Arguably, this was the case because the US police were notoriously sloppy in collecting the circumstantial evidence and because Simpson’s clever lawyers entangled the prosecutors in contradictions. Therefore, the practically damning evidence was completely lost in the process.

In the politically-motivated murder of Swedish Foreign Minister Anna Lindh in 2003, unlike in the unsolved murder case of Olof Palme in 1986, the police had recovered the murder weapon - a knife. No real fingerprints were found on it, but genetic ones were: skin particles, and DNA. In 2005, the DNA search for the murder of the Munich fashion czar Rudolf Moshammer was just as successful. All perpetrators were clearly convicted by DNA analysis.

It is interesting that the genetic difference between people from different continents is smaller than previously assumed: In the end, a single African may be more genetically similar to a single European or Asian than to another African. The DNA of two people differs by only 0.1%. Yet, in unrelated people, a changed letter is found about once every 1,000 genetic bases. However, this difference is sufficient to produce a "genetic fingerprint" that is unmistakable.