David deangelo advanced dating techniques

Two weeks later, the Zodiac shot San Francisco cab driver Paul Stine in the Presidio Heights neighborhood.Vallejo became the lead agency in the case because of the Lake Herman Road killings and the Ferrin killing.

Poyser said he hoped the same approach could be used if a complete profile of the Zodiac is obtained. It's a 50-years-old case." The use of public genealogy sites to track criminal DNA is relatively new.

"If we get a good profile, then you start tracking back," Poyser said. Prior to the case of the East Area Rapist, also known as the Golden State Killer, most investigations were limited to running DNA samples through state and federal databases that largely only contain DNA from convicted felons.

They originally were sent to the San Francisco Chronicle and the San Francisco Examiner, he said.

The third letter was sent to the Vallejo Times-Herald, but does not have an envelope with it, he said.

"Our Vallejo suspect is probably still the best lead," Poyser said of Allen.

"There are probably 30 different circumstantial things that point to him. He was extremely intelligent but a deviant dude." Allen largely was cleared as a suspect in 2002, when investigators obtained a partial DNA sample from the envelopes that didn't match his.

San Francisco police, who have been working on the case collaboratively with Vallejo, also have cards and ciphers sent by the Zodiac, he said.

Poyser said he believes the Zodiac Killer is no longer alive.

"They were confident they would be able to get something off it," Poyser said.

He said the envelopes had been sent to the lab a few months ago, before Joseph De Angelo, who is suspected of being the East Area Rapist, was caught after investigators used a DNA profile run though an open-source database.

A little more than six months later, the Zodiac struck again just a few miles from the first attack. At Lake Berryessa in Napa County, he attacked a young couple in September 1969.