A series of brutal and terrifying sexual assaults occur across northern Utah and Wyoming. 17 years later, new DNA technology reveals the perpetrator.

In 1973, two schoolgirls were found murdered in the Welsh village of Llandarcy. The killer's identity would remain a mystery until 2002.

In 1988, police discover the mutilated body of Lynette White. 25 years later, a ground-breaking DNA technique would finally lead detectives to the killer.

After a young woman was found beaten to death in Wisconsin in 1984, the killer evaded detection for decades. However, a revolutionary DNA method later revealed his identity.

In 1976, a woman was left for dead in her home in southern California. Despite a major manhunt, the violent killer avoided detection for over four decades.

In 1984, a young woman's body was discovered in a lane close to her home in Bath, England. How did police eventually track down the perpetrator of this heinous attack?

The murder of a respected teacher brutally attacked in her Pennsylvania home. Her death shocked the community, though it took 27 years for dedicated investigators trace her killer.

In 1986, in Kent, a teenage girl is on her way to the shops when she is attacked and sexually assaulted. Decades later, new DNA technology reveals the perpetrator.

In 2001, a student is attacked in Williamsburg, Virginia and months later the attacker strikes again. Finally, new DNA technology reveals the perpetrator.

In 1980, a young woman disappears and her body is discovered shortly after. Almost 40 years later, new DNA technology reveals the attacker.

In 2018, two paralegals were shot dead whilst at work in Scottsdale, Arizona. Four more victims were linked to the killing - who was the serial killer?

In 1979, two young boys came home from school to find their mother's dead body in the living room. Investigators set out to track down the killer with no firm leads.

In 1982, a woman is found shot to death near Lake Tahoe. 37 years later, ground-breaking technology would help identify both the victim and the killer.

In 1994, 42-year-old Le Bich-Thuy is found dead next to her home. Decades later, DNA and genealogy technology allow detectives to track down the killer.

After being reported missing, a young couple's bodies were discovered more than 60 miles apart. Dedicated investigators set out to find their killer.

69-year-old Evelynne Derricott is found brutally murdered in 2011. After the case goes cold, new DNA technology eventually leads detectives to the truth.

In March 2003, a lorry driver was found dead behind the wheel in Camberley, England. Police gambled on the revolutionary technique of familial DNA analysis.

In Colorado, in 1996, a young woman's body was found in an alley. After the case goes cold, advancements in genetic technology lead police to the killer.

On Valentines' Day 2007, police in Southern California were called to a particularly violent murder scene. Advances in forensic genealogy finally solved the case.

In 2001, a young couple were brutally assaulted in Salisbury, Wiltshire. Over a decade later, new DNA technology helped lead investigators to the attacker.

In 1999, hospital worker Jennifer Watkins was sexually assaulted and murdered. Two decades later, revolutionary DNA testing helps to solve this cold case.

In 1992, a woman is sexually assaulted in Sacramento, California by a man wearing a ski mask. This sexual predator continues to commit heinous crimes until new evidence exposes his identity.

When two teens are found dead in Montana, detectives suspect an infamous gangster might be responsible. But it will take 65 years to find the true culprit.

A small community in Utah is shocked when an elderly woman is brutally attacked in her own home. Detectives use innovative techniques to solve the case.

After decades of searching, Ohio detectives use ground-breaking technology to hunt down the man who abducted and sexually assaulted a 19-year-old woman.