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

A bloodstained shopping trolley holds the key to solving the case of a vicious assault. A distinctive pair of curtains, seen on a video call thousands of miles away, helps put a phone thief behind bars.

A discarded cigarette butt gives police the proof they need to find the murderers of a young father shot and killed in broad daylight. A used match found in a drainpipe identifies a arsonist who burnt a 400-year-old building to the ground.

A yacht is tracked by police as an organized crime gang uses it to smuggle deadly weapons into Britain and a recording of a prison phone call helps jail a bank cashier for arranging to steal an elderly couple's life savings.

A drug boss is put behind bars thanks to a paper trail from his dodgy property empire. A bank cashier helps convict a fraudster who's posing as a police officer, exploiting a vulnerable pensioner in a scam to extort thousands of pounds.

A train ticket and a chance encounter help hunt down a pair of hi-tech international fraudsters with links to the Russian underworld. A glass milk bottle gives police the evidence that seals a case against a violent offender.

An airport hire car provides the clues to the identities of a pair of South African hitmen who have come to the UK to brutally murder a private investigator in his home. A rare bottle of Caribbean rum helps convict a prolific burglar.

A discarded gun cartridge helps the police to convict a man who gunned down a fellow officer, and a packet of medication helps to lock up a gang of violent jewellery thieves.

A simple business card reveals the true identities of a gang of con artists, and a ripped-up, handwritten note holds the key to locking away two murderers.

A grainy video from a petrol station forecourt helps convict a gang of cold-blooded killers, and a criminal’s mobile phone finally connects an unscrupulous gang targeting the vulnerable.

A fingerprint from an old break-in solves a murder at the same factory months later. Elsewhere, a DNA spray means police can finally apprehend a prolific motorbike thief.

A hotel guest book gives police the names of an international drug smuggling network, and thieves who stole £20,000 of food from a factory are caught out by a car number plate.

A fingerprint on a fish and chips wrapper places a gunman in a rural location miles from his home, and a man’s laptop reveals that he is behind a luxury gift card fraud.

A jacket recovered from a suspect’s home has the DNA of two stabbing victims on it, and a fingerprint on a getaway car number plate snares an armed robber.

Fingerprints found after a break-in and brutal beating are enough to convict a man of murder, and crooks who burgled a man's home and started using his credit card are caught by CCTV.

Blood spatters found on a trench coat belonging to a suspect in an unrelated case of armed robbery links a callous killer to the murder of a wealthy pensioner.

A few spots of the victim’s blood on a blue shirt convict a murderer, and a rapper incriminates himself when videos he posts online about his drug dealing are seen by the police.

A blood-spattered hammer is the key to charging the prime suspect in a murder case, and a drug gang is brought down when one detective focuses on how the product is packaged.

A USB stick with information about illegal drugs is found at a respectable businesswoman’s house, and police crack down on the conversion of guns designed to fire blanks.

A single piece of paper found on top of a hidden fax machine gives police the number of a shipping container used to smuggle millions of pounds' worth of drugs from Thailand.

A hammer contaminated with the DNA of both victim and killer helps police solve a murder investigation, and a burglar is caught after photographing himself at the crime scene.