December 2000: 19-year-old Rachel Manning was murdered in Milton Keynes. Two men were wrongfully convicted, but new advances in forensics proved that evil always leaves a trace.
The Pittsburgh Police Force and the FBI raced against time to locate missing 13-year-old Alicia Kozakiewicz. The only trace that could be found to help with their investigation were cyber forensics which led them to locating her.
When the body of a child is found, Boston State Police have no leads, but with the help of the National Centre for Missing and Exploited Children, a trace is found.
Edinburgh, October 1977: Christine Eadie and Helen Scott vanish without a trace. The police never stopped hunting for justice, even changing the law to bring justice.
Digital forensics, traditional police work and a good old fashioned stake out stop a killer in his tracks, when all he's left is a digital trace.
When women start to go missing, the city of Baton Rouge goes into lock-down. Investigators and family members work together to find that illusive trace of evil.
Just as Baton Rouge starts to feel safe they discover a second serial killer is at work. However, when he leaves a trace at a scene, and the police find it, they get an unexpected breakthrough.
The body of actress Gemma McCluskie was discovered in the Regent's Canal, dogged detective work and detailed forensic examination lead police to her brother Tony.
Tracie Andrews purportedly witnessed the murder of her boyfriend, Lee Harvey, in a country lane on the night of 1st December 1996; but all was not what it seemed.
When a young couple were found executed in their home in October 2015, at first there were no apparent leads. The murderer, however, had left crucial evidence behind.
In late 1992, an attack led to an investigation which would last nearly a quarter of a century. Over time, DNA profiling helped to close a case which detectives feared would never be solved.
When a box containing human limbs was discovered in Florida, an investigation started that tested forensic capabilities, with detectives desperate to discover who the victim was.
When the body of a child is found, Boston State Police have no leads, but with the help of the National Centre for Missing and Exploited Children, a trace is found and the police continue with their investigation.
David Jackson left his home to buy beer and cigarettes. He was never seen again. For 15 years his disappearance remained unsolved, until one investigator broke the case wide open.
The murder of Lynette White led to the longest murder trial in British history at the time. Find out how police work and DNA eventually led police to her killer.
By September 1973, with three murders in just three months, South Wales Police realised they were looking for Wales' first documented serial killer.
Rachel O'Reilly was savagely murdered in her home, in what looked like a burglary gone wrong. A ground-breaking investigation finally put her killer behind bars.
15-year-old Janet Commins was savagely murdered, her body hidden in undergrowth. 40 years later, DNA profiling eventually helped to catch the killer.
After body parts were found in a Dublin city canal, a broad forensic investigation was needed to identify the victim, and lead police to those responsible.
The mutilated bodies of two women sparked a massive police manhunt. With advances in forensic science, investigators brought Ireland's only living serial killer to justice.
The murder investigation surrounding the death of a young, defenceless woman led police to another case, where the science of DNA profiling helped to unravel the truth.
A killer, who identified then murdered his victims, caused a manhunt which lasted nearly three decades. The science of DNA eventually led to his capture.
A popular, healthy, 60-year-old woman suffered a sudden, painful death. Detectives managed to trace the killer, despite their calculated and elaborate web of deceit.
A killer, who stalked and gained his victim's trust, enticed her to her death. Almost two decades later scientific advances brought the perpetrator to justice.