In 1997, 84-year-old, Ken Speakman was murdered and his prize gun collection stolen. Following an intense investigation British police were left stumped until the guns reappeared in a botched burglary, but it seemed nothing else linked the two cases.

In 2002, British police conducted one of the UK's first forensic investigations using mobile phone data and CCTV to help unravel the web of lies surrounding the grisly murder of heavily pregnant 27-year-old, Soumia Cullinane.

In 2013, the body of 59-year-old jeweler, Michael Griffiths was found tied up and dead in his burning Sussex home. Find out how British police used a valuable tip off to not only catch his killers but reveal that his torture and death were all in vain.

In July 1994, the naked body of 27-year-old Julie Clayton was discovered so badly disfigured that British police struggled to identify her. Desperate to catch her killer, technology used by Vogue magazine was drafted in with incredible results.

In 2008, detective Steve Smith was revisited by a case that had haunted the Met. Police for 7 years.

Vincent Brothers had a great job as the vice-principal at the Fremont School, an adoring wife Joanie Harper, and three children. One Sunday before church an intruder killed them.

Christian Longo appeared to be an attractive and charming family man. However, just a few days before Christmas in 2001, this picture-perfect family was destroyed.

Kathryn Darling was a 17 year old pregnant woman who was found dead in her apartment in 1976. Diane Holloway was 21 years old when she went missing in 1979. Her body was found 2 days later.

The 1971 case of Elijah Butler. This was the murder of a US Marine, home on leave to marry his fianc e, Geraldine. He was murdered four days after their marriage, his killer wasn't found.

In April 2004, Melanie McGuire and her husband Bill had been married for five years. They were raising two sons in a New Jersey apartment.