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.

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 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.

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.

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

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

In 1997, two women are sexually assaulted in separate attacks. Forensic evidence suggests the crimes are linked, but it takes over two decades to find the perpetrator.

On 24th December 1984, a body is discovered in a shallow grave. When another dead body is discovered police fear a serial killer is at work. The victims remained unidentified for decades before a new DNA technology gave them justice.

When a woman takes a genealogy test to learn what happened to her estranged mother, she is shocked to learn that her DNA has helped law enforcement identify a Jane Doe and identify the murderer of 4 other victims.

In 1981, a female high school student is found dead on the side of a road. Police work tirelessly on the case until new DNA technology exposes the killer.

In 1995, a masked man commits a series of sexual assaults at knifepoint. It takes more than 20 years for this serial rapist to be identified and then brought to justice.

In Alexandria, Virginia in 2016 a young female lifeguard is raped while working at a local pool. Police learn of a similar incident in Fairfax, Virginia 2 years earlier. It takes ground-breaking genealogy tools to find the perpetrator.

In 1977, the body of a young woman is discovered by blackberry pickers in Everett, Washington. The body is covered in flies and maggots. Police officers fail to identify the victim until revolutionary technology breaks open the case.

In 1968, 60-year-old Gwen Miller is brutally raped and murdered inside her own home. A devastating flood then halts the police investigation until ground-breaking science offers some new hope.

In 1998, a woman and her daughter are found brutally murdered, both shot in the head several times. The case goes cold for over a decade until genetic genealogy uncovers the perpetrator.

In December 1987, the nude body of a 17-year-old girl was dumped on the side of a rural road in Ohio. She had been raped and strangled to death. Genetic genealogy is called upon to help solve this violent murder.

In 1988, Janet Tinsley reports her 8-year-old daughter April missing after she fails to return home. Three days later, a man out jogging makes a gruesome discovery in a nearby ditch.

In 1963, the body of a toddler is discovered in the Keene Creek reservoir in Ashland County, Oregon, wrapped in a bundle of bedding. The child is determined to a white male, possibly having Down Syndrome. Despite the limitations of forensic science at the time, investigators are determined to find out who the so-called "Boy in the Bundle" is, and how he ended up in the water. After nearly six decades, developments in technology provide a major break in the case.

Niles, Michigan 1987, Terry Wood comes home to find his wife Roxanne lying dead in a pool of blood.

2001, Greeley, Colorado, a 7-year-old girl is walking to school with her 8-year-old brother when an unknown assailant snatches her off the street and bundles her into his car.

Fort Worth Texas 1974. 17-year old Carla Walker is kissing her boyfriend Rodney in his car when suddenly the door is ripped open by an unknown assailant.

High school student Kim Bryant is last seen outside a Dairy Queen restaurant. Three weeks later, her body is discovered by three teenage boys hiking on the outskirts of town.