Spotlight on: Sir Alec Jeffreys

When Sir Alec Jeffreys made the discovery that formed the basis of DNA profiling, he immediately saw the potential for uses in forensic and legal investigations. What he perhaps didn’t expect was the impact this single discovery would have on solving difficult paternity and immigration cases, catching criminals and freeing the innocent.

  • Last updated Jun 25, 2019 9:43:28 AM
  • Elizabeth Hurst

Name: Sir Alec Jeffreys CH FRS MAE

Current Role: Professor of Genetics and Royal Society Wolfson Research Professor at the University of Leicester.

Notable for: Developing techniques for genetic fingerprinting and DNA profiling. The methods developed by Jeffreys are now employed worldwide, most notably in forensic science to assist police detective work and to resolve paternity and immigration disputes. He became an honorary freeman of the City of Leicester in 1992, and in 1994 was knighted for services to genetics. Other accolades include the Albert Einstein World Award of Science (1996), Louis-Jeantet Prize for Medicine (2004), the Lasker Award (2005) and the Heineken Prize (2006).

Early life

In his childhood, spent in Oxford and Bedfordshire, Jeffreys showed a great interest in science, attributing his curiosity and inventiveness to his father and paternal grandfather, who held a number of patents. His father gave him a chemistry set at the tender age of eight, which Jeffreys embellished with extra chemicals—including a small bottle of sulphuric acid, which accidentally splashed, causing a permanent burn scar on his chin. He says he particularly liked making small explosions and examining biological specimens using a Victorian-era brass microscope, also bought for him by his father. Jeffreys made a small dissecting kit (including a homemade scalpel), which he used to dissect a bumblebee.

Though his parents were ultimately supportive of his early scientific exploits, they weren’t as pleased in one instance when their son dissected a dead cat he had found on the road while doing his paper round. As he dissected the creature on the dining room table, he accidentally ruptured its intestines, releasing a pungent smell that spread throughout the house and ruined Sunday lunch.


Jeffreys spent his early education as a pupil at Luton Grammar School and then Luton Sixth Form College. He won a scholarship to study Biochemistry at Merton College, Oxford, where he spent four years before graduating in 1972 with a first-class honours degree. Jeffreys decided to continue his postgraduate studies in Oxford, where he eventually completed his Doctorate of Philosophy at the University of Oxford Genetics Laboratory, where he narrowed his focus to study the mitochondria of cultured mammalian cells.

After he finished his doctorate, Jeffreys moved to the University of Amsterdam to undertake an EMBO Postdoctoral Fellowship. Here, he was one of the first to discover split genes alongside Dr Richard Flavell. His academic journey studying mammalian genes took him to the University of Leicester in 1977, where he remains to this day as professor of genetics.

His move to Leicester was born out of a desire to try running his own lab, and a well-timed phone call with Bob Pritchard, founder of the Department of Genetics. He agreed to come to an interview, put the phone down and asked, “Where the hell is Leicester?”, then rushed to find a map. In his own words: “I visited Leicester and I immediately fell in love with the department. I came as a temporary lecturer and I'm still here 32 years later, so it says something about the environment. I love it here.”

It was in his adopted hometown in 1984 that he discovered a method of showing variations between individuals’ DNA, inventing and developing genetic fingerprinting.

The discovery

What Jeffreys calls his “eureka moment” happened in his Leicester-based lab on September 10, 1984. He was looking at the results of a DNA experiment, and noticed that an X-ray film image showed both similarities and differences between the DNA of different members of his technician’s family—a pattern that was quite unexpected to Jeffreys. He quickly realised the potential implications of his discovery to identify individuals from the DNA visible in their fingerprints through variations in the genetic code. Talking with Jane Gitschier for PLOS Genetics Journal, he recounts his thoughts on that very first day.

“When I talked about it in a department seminar, and then speculated about what we could use this for, like catching rapists from semen—about a third of the audience fell over laughing. It sounds bizarre now because it's so blindingly obvious that you can use DNA for this, but believe me, back in the 1980s it was simply not there. The only reason I came up with the idea of DNA-based identification was that it just hit you in the face!

“So, within the first day, we saw identification, we could foresee forensic analysis if DNA survived in forensic specimens, zygosity testing in twins, paternity testing and immigration disputes. Just like drawing up a shopping list—if we could get this technology improved, what it could be applied to.”

Jeffreys’ expectation was indeed accurate. His method has become important for many of these uses in forensic science, helping police detective work and to resolve disputes over paternity and immigration. Despite originally being spotted with human DNA, the method also has applications for non-human species, such as in wildlife-population genetics studies.

Before his methods were commercialised in 1987, the laboratory in Leicester was the only place in the world that carried out DNA fingerprinting, and thus was inundated with enquiries from all over the globe. Jeffrey’s remembers “a complete avalanche of letters and phone calls; people were turning up at my home! […] I nearly had a nervous breakdown, but I kept going. It was an insane two years, 1985-1987, before the thing went commercial. We were the only lab providing any testing at all.”

DNA profiling and the law

In 1985, Jeffreys and his team developed DNA profiling based on typing individual highly-variable minisatellites in the human genome. The term refers to the initial test that types many minisatellites simultaneously. By focusing on a small number of highly variable minisatellites, Jeffreys’ team made the system of DNA profiling more sensitive, more easily reproduced and better amenable to computer databases. This improvement meant it soon became the standard system for forensic DNA, which is now used in criminal casework and paternity testing worldwide.

After the system was further refined by Peter Gill at the Forensic Science Service in the 1990s, the UK National DNA Database (known as NDNAD) was launched in 1995. Thanks to the highly automated and sophisticated equipment of today, modern DNA profiling can process hundreds of samples every single day. The current system considers 16 microsatellites plus a marker that determines sex and gives a discrimination power of one in over a billion.

Under British law, anyone arrested in England, Wales or Northern Ireland now has their DNA profile taken and stored on the database whether or not they are convicted (though slightly different rules apply in Scotland). The national UK database now contains the DNA information of almost five million people.

First legal uses

Jeffreys’ method was first put to use in 1985 to help in an immigration dispute to confirm the identity of a British boy who was threatened with deportation because immigration authorities alleged he wasn’t the biological son of a Ghanaian family. The recent DNA discovery was also to resolve the case, as results proved the boy was closely related to other members of the family.

Jeffreys looks back on this first victory fondly: “That was the first DNA case tackled anywhere in the world, and it is still my favourite case because I was there at the tribunal where they dropped the case against the boy, when the mother was told—and just the look in that mother's eyes! She had been fighting the case for two years.”

In a case a little closer to home, DNA fingerprinting was first used in a police forensic test to help solve the case of Lynda Mann and Dawn Ashworth, who had been raped and murdered in Narborough, Leicestershire, in two separate incidents during the 1980s. Jeffreys’ methods were used to identify and convict Colin Pitchfork after samples taken from him matched semen samples found on the girls’ bodies. Without this piece of evidence, British authorities believe that an innocent man would have instead been convicted.

Another high-profile use that employed Jeffreys’ research was the 1992 case in Germany to confirm the identity of the Nazi doctor Josef Mengele, even though he had died in 1979, by comparing DNA obtained from his exhumed skeleton with DNA from his mother and son, in a similar fashion to typical paternity testing.


Jeffreys himself spoke out in opposition to the current use of DNA profiling, while at the 2002 British Association’s science festival in Leicester. In particular, he’s concerned about how the genetic profiles of suspects are still stored by authorities after they have been cleared of any crime. He says the practice is highly discriminatory and calls for measures to be taken to safeguard against particular individuals or groups being targeted. He suggests the creation of a national database that stores the profiles of the entire UK population, which would be managed by an independent body: “If we're all on the database, we're all in exactly the same boat—the issue of discrimination disappears.”

Jeffreys told the BBC: "With the current DNA database of criminals, there's been a recent extension to include suspects who've been convicted of no crime at all—I think on the assumption that at some stage in the future these people may commit a criminal offence.”

"My other concern is that some forensic scientists are now beginning to look for physical characteristics; genetic determinates of hair and eye colour, ethnic group as well—to get some indication of the physical appearance of a person where you have no clear suspect.” 

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