Harvard Hero Moments - DNA Testing

Harvard Hero Moment #4: “CSI Leicester”: how one man’s mission to better understand family trees changed the justice system forever

Lorna Hughes

17 Sep 2019

When geneticist Alec Jeffreys began a new line of research at his Leicester University lab in 1984, he had no idea of the revolutionary discovery he was about to make.

Jeffreys was attempting to trace genes through family lineage. During his research, he’d discovered a DNA fragment which showed up on different chromosomes in the cells of men and women. He wondered whether this apparent glitch could be unique to an individual, so he created an experiment to see if he could count those repeats in different people and their relatives.

I won’t go into the technical detail of that experiment here – if we truly understood that level of scientific genius, we’d all be off transforming the world’s view of the human body. But once the experiment was set up, Jeffrey left his lab over the weekend and hoped he’d come back on Monday to results which would help him study hereditary diseases.

When he returned on Monday morning, he and his research team were disappointed. Rather than any clear patterns, the experiment showed an apparently sporadic bunch of blobs and lines.

In his own words, “My first reaction was ‘God, what a mess.’” But then he looked closer and tried to make sense of what he was seeing. In doing so, Jeffreys changed the course of DNA analysis and forensics. And he made technology an undeniably vital part of the justice system forever.

A discovery that changed everything

What Jeffreys was staring at was a sequence of bars, each representing different numbers of DNA repeats in the various individual test subjects. His most important finding was that every individual in the sample had a different bar code and could be identified with incredible precision.

Jeffreys could even distinguish establish links between families. For example, some bands of DNA supplied by one of his technicians were not hers: they were from her parents. But Jeffreys could still link it back to her with previously unheard of certainty.

The lab realised what they had, and DNA fingerprinting was born.

Since the discovery, the technology has become the primary, and most reliable, way of identifying an individual – using their, or their relatives’, unique DNA patterns to place them in a certain place at a certain time. It has been used in immigration and parental testing, as well as the conservation of non-human species. And, of course, it has been used within crime scene investigation.

Almost every nation now maintains a database with genotype information from criminals. The UK’s was founded in 1995, and all 50 states in the US require a sample to be collected from every convicted felon. Globally, the technology has enabled millions of cases to be solved, including historic unsolved murder or assault cases.

Put simply, if it wasn’t for the work of the now Sir Alec Jeffreys and his team, these cases may have remained unsolved, their perpetrators would never have been caught and victims and their families would have received no justice.

Leaving a world-class (genetic) inheritance

DNA fingerprinting is a once in a generation discovery that alters the way we see the human make-up and, in practical terms, changes crime scene analysis, forensics, law and justice forever.

It is the kind of technological innovation which truly changes the world. Which is why it’s absolutely one of my Hero moments in tech from the last 40 years.

Read more about Sir Alec John Jeffreys and his team’s work here.