This Day in Tech History

On This Day . . .

A “Eureka” Moment

DNA Strands

September 10, 1984: Genetic Fingerprinting Discovered

Sir Alec Jeffreys of Leicester, England noticed and deduced that DNA is a unique item from person to person and could possibly be used to identify someone. Hence, Genetic Fingerprinting was born. Alex was originally working on a way to determine heredity of illnesses when he made this discovery.

Sir Alec Jeffreys

Sir Alec Jeffreys

On Monday Sept 10 of 1984, at 9:05 am Jeffreys had a “eureka moment” after looking at the X-ray film image of a DNA experiment which unexpectedly showed both similarities and differences between the DNA of different members of his technician’s family. Within about half an hour, he realized the possible scope of DNA fingerprinting, which uses variations in the genetic code to identify individuals.

Not only could he see many mini-satellites as he had expected, he also saw that the mini-satellites for one individual varied greatly from one person to another. As such, the DNA patterns for one individual appeared to be unique. This meant that DNA could create an exclusive biological identity for every person, with the exception of identical twins, who share identical DNA “fingerprints.”

He called his staff together and they began a brain-storming session to find uses for the technology they had stumbled on. Paternity cases were an obvious example, as was the identification of criminals. “But then we thought, how about crime scene samples. Could we get DNA from blood left behind after murders or robberies?”


Today this seems a silly question, attuned as we are to the marvels displayed in CSI Miami and the rest. But in 1984 no one knew how stable DNA was. For all Jeffreys knew, it could break apart rapidly after a cell had died, making crime scene sampling impossible.

“So I spent the next two days cutting myself and leaving blood marks round the laboratory. Then we tested those bloodstains and found that their DNA was intact.” Thus the genetics laboratory of Jeffreys was not only the birthplace of DNA fingerprinting; it became the first setting for a DNA crime scene analysis.

Before his methods were commercialized in 1987 his laboratory was the only center carrying out DNA fingerprinting in the world, and during this period of about two or three years it was very busy, receiving inquiries from all over the globe.


DNA fingerprinting was first used as a police forensic test to identify the rapist and killer of two teenagers, Lynda Mann and Dawn Ashworth, who were both murdered in Narborough, Leicestershire, in 1983 and 1986 respectively.

Lynda Mann & Dawn Ashworth

Lynda Mann & Dawn Ashworth

Colin Pitchfork was identified and convicted of murder after samples taken from him matched semen samples taken from the two dead girls.



This turned out to be a specifically important identification for without it, British Authorities believe that Richard Buckland, the main suspect, would have inevitably been convicted. Therefore, not only did Jeffrey’s work in this case prove who the real killer was, but exonerate someone who likely would have spent his life in prison.

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