A 20-year-old woman sets out on her bike and never returns; her body found just a few miles from her house in Snohomish County, WA, with a gunshot wound to the head. Years go by without any hard evidence or leads, until a new generation of investigators and modern technology breaks the case.

In 1982, 37-year-old Navy lieutenant Lee Hartley is murdered while deployed out to sea. Cause of death? Arsenic poisoning. Investigators discover Lee had more than his fair share of enemies aboard the ship. But it takes years before investigators discover what really happened to Lee and who, ultimately, was behind this brutal murder.

A building manager finds the violated and lifeless body of a young woman in the bathtub of her first apartment. When questioned, an ex-con living downstairs lies to police. But the lies alone do not prove murder and the case goes cold. Then, a new forensic tool examines the old evidence.

A murder victim’s final moments are caught on tape; the crime scene looks like a clear robbery-murder. Text evidence at first points to a jilted lover. Soon, police identify a second suspect with a possible motive of deadly revenge. Forensic technology and DNA evidence combine in an attempt to make the case.

A mortally wounded woman crawls to call 911. Her ex-husband, who wants to be free of her, gets a hard look from police. But he says he has an airtight alibi for the exact time of the murder. The intricate forensic science of ballistics is brought to bear to and draws a direct connection to an unexpected conclusion.

A deeply religious librarian, wife and mother named Gail Fulton is shot execution style in the quiet suburbs of Michigan. Surveillance video reveals it was trio of killers that took her down. Eventually, detectives get a break: a handwritten note. But will it provide enough clues to catch the mastermind behind this horrific killing?

In 1990, three sex workers are brutally murdered and left along the banks of the Spokane river. A serial killer was on the loose—and detectives had few clues. Animal hairs, fibers and a fingerprint were found, but for years the perp was never identified. More than 20 years later there’s a break in the case- and an arrest is finally made, but no one could have ever imagined who was behind this sinister crime.

He is a criminally charged sex offender and a murderer who attacks in a terrifying rage. This predator manages to evade capture for years, but he leaves a critical piece of evidence behind – his palm print. Detectives are determined to do whatever it takes to put a name and a face to the print.

An early morning house fire kills the only doctor in the small town of Iaeger, WV. An arson investigation quickly leads to the arrest of Jason Lively, the son of the doctor’s long-time nurse. But when Jason’s alleged accomplice walks free, the prosecutor is worried this might have been a miscarriage of justice.

On a brutally cold winter night in 1984, a young woman is found viciously murdered on the side of a rural Wisconsin driveway. The victim, Traci Hammerberg, had been out with friends for a night of drinking and partying. What happened? Detectives initially have plenty of suspects, but the investigation would remain unsolved. Until nearly three decades later, when forensics from an unrelated crime helps breaks the case.

A hearing-impaired 77-year-old on a road trip is attacked by a thief and shot to death. Why? Because the man cannot hear his assailant’s demands. Random murders are among the hardest crimes to solve, but investigators are determined to bring this killer or killers to justice. Can advances in ballistics testing crack the case?