LA Forensics: Mysterious Confession

In 1975, when Lancaster's soon-to-be daughter-in-law, Jeanette, first came forward and told the police about his chilling confession, there hadn't been enough evidence to arrest the 49-year-old cab driver.

Fast forward 28 years to the spring of 2003. The police had two witnesses and a male DNA profile recovered from one of the victims. They just had nothing to compare the profile to.

What Bengtson and Flores needed to cinch the case was a DNA sample from their suspect that matched the one taken from Lois Petrie. The problem was they didn't have a sample of Lancaster's DNA.

There are basically four ways for law enforcement officers to get a suspect's DNA. One is from a prison record. Since the 1990s, many of the country's prison systems have taken DNA samples from convicted felons and entered them into databases. But Lancaster had never even been arrested, much less convicted of a felony.

The second way to get a suspect's DNA is with a search warrant, but in the Petrie case, the Los Angeles District Attorney's Office decided that the statements of two witnesses who had heard Lancaster make incriminating remarks about murdering four women weren't enough to get a search warrant.