The Green River Killer attacked prostitutes in Seattle in the early 1980s. He strangled them, and weighed their bodies down with rocks before throwing them into the river, where all evidence of the killer was washed away.

Police set up the Green River Task Force; they spent $12 million on the case, and interviewed 15,000 people. Finally in December 2001, a Seattle man was charged when new DNA evidence appeared to link him with four of the murders.

---

In 1960s San Francisco a spate of apparently random killings were accompanied by letters to the local newspaper. Each chilling note was signed using a different symbol of the Zodiac. Despite years of searching, the police never prosecuted anyone for the murders.

When a series of shootings occurred in New York twenty years later, they were accompanied by letters with Zodiac markings, and many people feared the Zodiac killer was back. But 26-year-old loner Heriberto Seda's fingerprints were found on one of the letters. He was not connected to the San Francisco Zodiac killings, which remain a mystery to this day.

---

In the 1960s in London, a murderer preyed on prostitutes, strangling them, then abandoning their bodies in busy public places. A vast police search was set up for the man who became known as Jack the Stripper, because his victims were always naked.

The only evidence the police had were some flecks of paint found on the bodies. After more than a year a 45-year-old security guard was identified, who owned a van, and patrolled near a paint workshop where paint was found to match that on the bodies.

Before he could be brought in, the security guard committed suicide. To this day, his name remains a secret, to protect his family after his death.