David Threlfall: ‘DNA fingerprinting is a very British invention!'

Shameless star David Threlfall talks to What’s on TV about the remarkable true story which saw two British men change the face of policing.

ITV’s new two-part drama, Code of Killer (Monday), sees David Threlfall play real-life detective, David Baker, a pioneering policeman who joined forces with DNA scientist, Alec Jeffreys (John Simm), ultimately leading to the first ever conviction of a vicious double murderer, using DNA evidence!

Can you set the scene for the dramatisation of this incredible true story?

"It concerns the unsolved murders of two teenage girls, three years apart in 1983 and 1986. They happened in the same area of Leicestershire where Alec Jeffreys was investigating DNA genetic fingerprinting. I play DCI David Baker, who suddenly wonders, could we utilise DNA testing to solve these horrific crimes? It was the first use of DNA in crime solving anywhere in the world!"

Did David Baker have something of a Eureka moment?

"That’s exactly what I’m describing! Biochemist Alec Jeffreys (John Simm) was using DNA genetic fingerprinting in immigration cases. David thought this process could work in crime. It a very British invention in that sense. The configuration of the two men has resulted in something that’s used worldwide now."

It must have been considered risky at the time?

"I think, for David, it was logical to use DNA. He was also one the first people to use tape recorders in police interviews and computers to correlate information. Until then everything was on rolodexes."

How much pressure were David and his police team under to catch the killer?

"The first murder had never left his mind, but by the time the second murder happened in 1986 the operation had been scaled down from about 70 people to six. Also, around that time there had been another five murders in that area and resources were stretched. So there was definitely some pressure."

There was also the issue of a local lad falsely confessing to the murders, wasn’t there?

"Because the DNA testing was new, David had to drive through the resistance to it, both from the people above him and his co-workers. Sadly these detectives see terrible things, and David had to convince them, even though someone had confessed to the murders, science said otherwise, and that they still needed to find the perpetrator."

And they did…

"Remarkably this pioneering DNA testing wasn’t only used to convict the perpetrator of these terrible crimes; it was used to prove someone’s innocence. It’s chilling to think about."


Elaine Reilly
Writer for TV Times, What’s On TV, TV & Satellite Week and What To Watch

With twenty years of experience as an entertainment journalist, Elaine writes for What’s on TV, TV Times, TV & Satellite Week and www.whattowatch.com covering a variety of programs from gardening and wildlife to documentaries and drama.


As well as active involvement in the WTW family’s social media accounts, she has been known to get chatty on the red carpet and wander into the odd podcast. 

After a day of previewing TV, writing about TV and interviewing TV stars, Elaine likes nothing than to relax… by watching TV.