Police run down more than 11,000 leads before coming up with a suspect in the murders of three girls. The abduction and strangulation of a woman continues to baffle investigators.

With access to the SFPD's work, including saliva samples, we reevaluate the case of the Zodiac Killer who began terrorizing California in the late 1960s--one of the first to send clues to the media.

Cops close in on a serial killer with the help of the Internet. And a drug trafficker jumps bail, goes into the bike shop business and helps pioneer the sport of mountain biking.

A former cop is a suspect in the murder of two nurses. A blow to the head leaves strange markings. Police hope that DNA will help track down the man who stabbed and killed a woman.

In the 1980s, a serial killer prowled the posh streets of Orange County. Police were unaware of the serial attacks until 1996, when DNA revealed the killer's secret and they linked four murders to a single DNA profile.

A thumbprint connects two separate murders and it is later discovered that the suspect had a strange fetish for women's lingerie. Then, an elderly woman is found murdered in her bed and the only evidence is a single strand of hair.

A mother is suspected in the murders of two of her daughters, when her third daughter finally convinces police to reopen two cold cases.

LA homicide detectives take a bandit who gunned down two police officers into custody. A suspected killer has an identical twin. Police suspect that a former cop committed the murders of two nurses.

A murderer's saliva helps seal his doom. Police crack a cold case with a DNA sample. An arson investigator is suspected of setting fires. A man is convicted of raping and murdering his neighbor.

Detectives track a man who murdered his wife after he's convicted of killing his third wife. A papergirl goes missing. A killer boasts to cellmates. Investigators probe the murder of a pregnant woman.

An undercover agent proves a wife had arranged a murder-for-hire. A man claimed his estranged wife committed suicide. Police solve a murder when divers find a skeleton.

A detective works for years to nab a man who murdered his wife. Years after the murder of a gas station attendant, detectives get a lead. A New Orleans police officer goes undercover on a riverboat.

In 1982 and '83, Seattle's Green River Killer stalked prostitutes like game. With 49 victims, he could be the deadliest serial killer in U.S. history. Then, police discover the badly burned remains of a woman, her skull smashed into 97 fragments.

The murder of a man leads police on a long chase for a man who's suspected of identity theft and bears a rose tattoo. A sheriff tries to get a mother to confess to killing her two babies.

Police must wait nearly 30 years before advances in DNA technology give them the chance to convict the killer of a young hitchhiker, and Philadelphia police wage a 16-year hunt for the man who raped and killed a 10-year-old girl.

Detectives from three different departments in Westchester County, NY team up to track down a serial killer. A man known as the Bus Stop Rapist becomes the lead suspect decades after a woman is found murdered under a hotel bed.

Police crack a cold murder case when a woman calls and says her boyfriend is the killer; and the 1998 murder of a woman provides clues to the '88 murder of actress Myra Davis.

Testimony about larvae growth helps convict a murderer. The murder of a girl remains unsolved. A police officer goes undercover to gain a confession. A man goes on trial after a body is found.

A killer's plan goes awry. A reporter helps crack a murder case previously ruled an accidental death. Police obtain DNA evidence from a cigarette butt. A mother is convicted of killing her daughter.

Testimony about the growth of larvae in dead bodies helps convict the man who stabbed a couple to death and strangled their 4-year-old daughter in 1993.

After 23 years, investigators track down the killers of an Atlanta policeman when the ex-wife of one of the killers phones in a tip. A mother keeps the skeletal remains of the daughter she killed.

Undercover agents conduct an elaborate sting to solve a murder case that had gone cold for years. Detectives from three different departments team up; the "Bus Stop Rapist" becomes a suspect.

A woman who takes down the license plate number of a car that had been following her helps police solve the murder of another young woman.

The testimony of three inmates helps convict a man who killed a woman and a sex addict is a suspect in the murder of a neighbor. Cops close in on a serial killer with the help of the Internet.

A prostitute helps police track down a serial killer. Undercover agents acting as mobsters solve a murder case. A series of brutal rapes goes unsolved until a fluke audit of a license plate number.