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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

A 70-year-old retired veteran is found dead on his boat after a bad sea storm. Detectives discover he was killed during an attempted robbery after winning $400 in keno.

A Texas ex-con resolves to live a clean life after his release from prison. When he’s later arrested and convicted for a bloody murder, he insists he’s innocent. From behind bars, he’s determined to use forensic science to prove his case.

Patients at the VA hospital in Clarksburg, WV, keep dying after experiencing shockingly low blood sugar levels. An investigation into their deaths reveals the patients were injected with lethal doses of insulin.