The Incredible True Story Behind Code Of A Killer

The gripping crime drama tells the story of a historic case and scientific development.

Starring David Threlfall as Detective Chief Superintendent David Baker, the series is set between 1983 and 1986 and follows DCS Baker as he investigates the murders of two schoolgirls in neighbouring Leicestershire villages three years apart.

At the same time and just a few miles away, Dr Alec Jeffreys (played by John Simm) was working at the University of Leicester who invented a technique to better understand and read a person’s unique genetic fingerprint and DNA profiling.

“We knew we were onto something right back at the beginning, back in September ’84 but just how big it would get we had no idea,” Jeffreys — who was later knighted for his services to genetics — said in an interview.

The series follows the two men as their investigations collide, with Jeffreys’ discovery aiding Baker in the historic first-ever DNA manhunt. The investigation also resulted in the first conviction based on DNA fingerprinting evidence, as well as the first person to have innocence established by it.

Not only was the series based on the actual events but the actors were also given the opportunity to work closely with the real men they were playing to portray the events as accurately as possible.

In an interview for the series, Threlfall described DCS Baker as “very straightforward and honest”, and explained that though he was a man of few words he had no issue letting the actor know if something was or wasn’t accurate in his portrayal.

“Having the real thing there is a great guide to helping you with a choice,” Threlfall said in the chat. “If you didn’t have the person there you’d be imagining, well would they say that or do that? When you’ve got the real one he’d say, ‘No I wouldn’t’. I’d always go with the real thing.”

While Threlfall made use of the real DCS Baker as a reference, his co-star admitted that he went a very different route to embody the role of Sr Jeffreys as realistically as he could.

“I didn’t meet him beforehand,” Simm said, “I’m portraying him in the early '80s and I didn’t want to pick up any traits that he had now as an older guy, so… thankfully there’s loads of footage of him… and so [I] tried to sort of do him justice.”

While Simm thought it was important to try and get his role as spot-on as possible, Jeffreys had sympathy for the actor.

“I feel sorry for the poor chap, he’s got to get in my head for the duration of filming,” he said, laughing.

You can watch all three episodes of Code of a Killer now on 10 play