We all sit and watch the TV, tutting and saying "That wouldn't happen," but what do police crime dramas always get wrong?

"Three main things," reports retired Detective Inspector Steve Gaskin.

"Senior police officers are not angry all the time, which is how its always portrayed.

"The sergeant assisting the senior investigating officer is not thick." (Take note, Morse and Midsomer fans.)

morse
Morse, and TV hits like it, raise unrealistic expectations of investigative success, according to Steve Gaskin

"In fact, he's often the focal point of the inquiry, so he's got a lot of facts, names and contacts in his head.

"Finally, the speed by which you see these cases get solved by forensics is completely unrealistic.

"Every exhibit has to be examined thoroughly and ethically. Science is just not that quick, and these dramas do raise false expectations."

Can You Think Of Anything Else That Always Seems Completely Unbelievable? Let Us Know Below...

TV dramas may not always get it right, but sometimes they influence real life. Gaskin reports that, in his day, "it was always the Flying Squad. And then, out of nowhere, it became... The Sweeney. And has been ever since."

According to Gaskin, the nature of crime hasn't changed in his time - "people are still people, as they always were" - but the tools of investigation are almost unrecognisable. What was the biggest shift?

"The hunt for Peter Sutcliffe changed everything about how police investigate. Everything was paper-based before that, with thick binders of police statements and exhibits.

"It turned out Sutcliffe had been in the frame five times before he was caught, because A wasn't talking to B, and everything was stuck in a big binder.

"So, after an inquiry, they built HOLMES - the Home Office Large Major Enquiry System, which was IT-driven and a revelation. They also put somebody in charge of incoming information, and somebody in charge of victims' relatives.

Gaskin, a retired detective police inspector who now arranges corporate events inviting members of the public to investigate real cases using proper tools of the trade, was himself an attending police officer on one of the cases featured in the second series of Fred Dinenage: Murder Casebook, which uses forensic science to delve into some of the archive's most perplexing cases.

peter manuel
Peter Manuel has remained a source of fascination long after he was hanged for his crimes in 1958

But he remains fascinated by one of the higher profile cases featured in the programme, that of Scottish serial killer Peter Manuel, who was convicted of seven murders at the age of 31, but was believed to have killed many more. Mary Bell, John Straffen and Raymond Morris (The Cannock Chase Murders) are also featured. But back to Manuel...

"He returned to the scene of the crime, fed the cat, and cooked himself a meal. Extraordinary," reflects Gaskin, who has also studied criminal psychology.

"My own theory is that he was brought up on a diet of American gangster films, and a childhood of abuse and had some very strange ideas in his head."

With his experience, how much does what would-be criminals watch on TV and film influence how they behave?

"There are two schools of thought, the nature and nurture arguments. All I can say is that there is evidence that there are some people who have a propensity to be influenced. But does that mean everyone else should be deprived of entertainment that has no effect on them? That's for someone else to debate."

Fred Dinenage: Murder Casebook 2 continues on Sundays at 10pm, on the Crime & Investigation Network (Sky 553, Virgin 237). Watch the trailer below...