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?

The unexpected and mysterious death of a health-conscious woman triggers an investigation into what killed her.

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.

When a beautiful college student is stabbed to death in her Knoxville apartment, suspicion immediately falls on her roommate. A bloody shoe print left by the killer exposes a murderer with no history of violence and no reason to kill.

After a 79-year-old woman is found shot to death in her home, shell casings and a high-tech database reveal the unlikely killer.

After the brutal slaying of a young couple on a road trip, the victims' families begin receiving disturbing letters.

Someone targets members of law enforcement in a peaceful Texas county. Numerous suspects emerge, and murders continue as detectives race against time. Finally, a single bullet casing uncovers the bizarre reason for which the killer wanted revenge.

The body of a 24-year-old criminology student is found wrapped in a blanket alongside a desolate Road in Brooklyn, New York. Police zero in on the bouncer at a SoHo bar.

July 4th weekend leads to a tragedy for a California family. To catch a killer, detectives utilize an unorthodox technique—analyzing bug fragments—to help put a murderer behind bars.

An insurance agent is shot execution style in his office in broad daylight, but the killer left no fingerprints and there was no murder weapon found at the scene… Then, investigators discover a critical clue invisible to the naked eye that cracks the case. (also marked as S1:E12)

A healthy, young mother mysteriously dies after a minor traffic accident triggering an investigation to find out what caused her death.

A massive explosion claims the life of a California farmhand. Authorities think it’s an accidental death, but analysis of debris shows it’s a bomb. Investigators have few suspects until they hear ominous rumors about a jealous rage.

Three Indiana construction workers are found shot dead at a work site. Detectives find few suspects, but have one key clue: one of the killers stepped in dog feces during the murders. If detectives can find his shoes, they’ve got their man.

An extremely successful California career woman keeps falling ill and doctors can’t determine why. When she dies, they still have no explanation, until they find a key figure in her life who has been lying about his past.

When a 23-year-old Marine dies in his bedroom, doctors initially believe a heart attack is to blame. When arsenic is found in his organs, his wife is charged with murder; a sharp attorney and toxicological testing uncover the truth.

When an 18-year-old girl is abducted while talking on a payphone, forensic evidence found on her clothing points police in the direction of a suspect who shockingly confesses that he didn't act alone.

When a Yale student mysteriously vanishes days before her wedding, investigators comb a secure research lab for evidence.

Police race to find a serial killer terrorizing a small Texas town.

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.

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.

An Illinois mother and her two young children are brutally murdered in their beds. Lurid threats are spray-painted all over the walls of the crime scene. Detectives discover death threats sent to the family, exposing an unlikely killer.

A young Texas teenager and her boyfriend are brutally attacked on Valentine’s Day; she is found dead while her boyfriend escapes. The case goes cold for nearly 50 years before a new forensic test exposes a family man with a dark secret.

A young single mother is abducted from a gas station and later found stabbed to death near an oil field. Detectives use shoe and tire impressions to weed out numerous suspects and find the killer.

In the story of a Los Angeles kidnapping, ransom and murder ring, retired scientists use sonar equipment to locate victims at the bottom of a reservoir.