When the search for a missing woman becomes a murder investigation, a baseball cap and DNA on a discarded beer can help detectives find her killer.

Two young women are shot dead in Birmingham on New Year's Eve. But it takes an audacious undercover mission for police to infiltrate rival gangs and find the moment of proof.

Police are left confounded by a serial burglar's Houdini-style disappearing act. But a single piece of information brings their game of hide-and-seek to a sudden end.

Police suspect foul play after a meet-up goes wrong. But it takes toxicology tests to reveal the deadly cocktail that convicts a killer.

Two men heading to a business meeting are kidnapped and forced to transfer a large amount of company money. Police unpick a web of calls and CCTV to find their moment of proof.

When a missing woman is found dead, family and friends raise suspicions about her boyfriend. But police need hard evidence that he was involved. And they eventually get it.

Two people die in an arson attack on their home, but police can't get a DNA profile from matches left at the scene. Then, an eagle-eyed detective clocks a problem with the CCTV.

An organised crime gang supplying large quantities of drugs is almost impossible to uncover. But painstaking surveillance leads police to the kingpin, bringing down the operation.

When a child goes missing, police have few leads. They have a suspect but not enough evidence to prove anything. Eventually, a torn-up cheque gives them their moment of proof.

When an unconscious man is stamped on, there's no CCTV. But can a footwear specialist looking at the bruising on the body help identify the shoes worn by the killer?

A fatal house fire turns suspicious two years on when it emerges the victim was visited by a stranger the night his home was destroyed. Will a plane ticket give a moment of proof?

A reclusive millionaire is found murdered in his home in west London, and police find hundreds of thousands of pounds in cash still there.

A jacket left behind in a stolen car carries the DNA to prove who was driving the vehicle. And a witness gives police key evidence from 30 years ago to crack a cold-case murder.