Line of Duty: Series creator Jed Mercurio reveals his secret source

"This series concentrates particularly on the new world of police interviewing techniques," says Mercurio

For the last series of Line of Duty Jed Mercurio relied on anonymous tips, retired officers and online blogs for his police advice. Now Mercurio’s mole is on the force as a senior serving officer. “He made contact with me after the first series — he was actually someone I was in school with,” he reveals. “He’s a police inspector in exactly the right position to be the ideal advisor, senior enough to understand the intricacies of procedure, but near enough to the coalface that he understands the day-to-day issues beat bobbies face.”


Procedure is still at the heart of the show, while almost every other tec show claims to be accurate — admittedly Sherlock not so much — most cut the kinds of procedural corners that would see an officer facing a Formal Conduct Hearing at force HQ.

“The programme makers aren’t ignorant of procedure,” Mercurio points out. “I watch cop shows, and I’m constantly banging on about witnesses or suspects being interviewed without a solicitor. That’s just budget — having to cast someone is extra money that could be spent on a really cool car chase. It’s fine dramatically but it’s not real life.” This series concentrates particularly on the new world of police interviewing techniques. TV’s greatest cop show trope is the nice cop/nasty cop interrogation — in real life, Mercurio explains, this sort of interview would be thrown out of court.

“You can’t have a police officer march into the room, bang the table and say, ‘Tell us. Did you do it?’” he laughs. “That just can’t happen in the real world.” Mercurio instead follows police interview guidelines issued in 1990 after a flurry of false confession scandals. Officers shouldn’t force a confession, shouldn’t pay attention to signs of anxiety in a suspect (it doesn’t correlate with lying, it turns out) and instead ask open ended questions then go back over the details again and again to find gaps or inconsistencies in the story. As an example of that: being asked to give your account of events in reverse, from the end to the beginning, is easy if you’re telling the truth, but tricky if you’ve created a lie.

Jed thinks this makes for stronger psychological drama. “They’re more like courtroom drama, where everybody is making sure that procedure is being followed and they’re not burrowing down a kind of legal trap,” he says. “It adds to the tension and drama — you see people having to think on their feet, working out how to get to the truth.” 

Line of Duty starts tonight at 9:00pm on BBC2