A DNA hit. Scientists tell police this is the killer of Melanie Road.

Even forensic scientists were saying, this has got to be the daughter of your offender.

It's just really, really strong match.

Julie Mackay gets tough with suspects who refuse to give samples.

We'll hunt you down like a long dog until we get your DNA. Don't expect that you just

saying no, I don't want to. We'll say, well that's okay then because how do I know that you're not the murderer?

And a fingerprint is found on a key exhibit.

Where the blood was on the shoe and on her foot,

that at some point the shoe had been taken off and put back on.

You're a detective investigating a cold case murder,

the killing of 17-year-old Melanie Road in 1984.

The killer just disappeared in the moments after. And despite leaving a

blood trail and 27 years of investigation, you still don't know who the murderer is. But someone

has called in to the inquiry, offering a name of a man who admitted the killing. So we did some

research on him. He was known to police. He'd had some

mental health issues, but he was not on the DNA database. So therefore, we needed a DNA swall.

There's a problem, kind of a big problem. The suspect is dead, and his funeral is in the next

48 hours.

This is what faced Detective Sergeant Julie Mackay and the cold case team in 2011.

So we tracked him down to a funeral parlour in Bath, and then the next thing is, so these are like your little ethical dilemmas.

So what do you do? You can't just go and take a swap from somebody who's dead.

You need to get some consent from somebody,

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