Police hunting Zodiac Killer deploy DNA technique used to identify suspected Golden State Killer

US detectives are using the same DNA tracing technology employed recently to arrest the suspected Golden State Killer as they hunt for another of the country’s most infamous serial killers.

Police in Vallejo, Northern California, have sent letters written by the so-called Zodiac Killer for analysis at a private laboratory in a bid to build a better profile of the murderer who shot and stabbed to death at least five people in the 1960s.

They hope DNA may be found on stamps or envelopes and could then be cross-referenced with online databases.

Detectives investigating the Golden State Killer ran DNA through an open-source genealogical website before the arrest of former police officer Joseph James DeAngelo, who is alleged to have committed at least 12 murders and rapes in California between 1976 and 1986.

Investigators in Sacremento uploaded DNA collected at one of the crime scenes to the website and found a partial match to a distant relative of DeAngelo. They painstakingly constructed a family tree dating back several generations before they zeroed in the 72-year-old.

The process raised concerns among privacy campaigners, who are worried about future abuses, but detectives investigating the Zodiac Killer say the technique could help solve one of the most notorious cold cases in the country.

The Zodiac Killer sent taunting letters to local newspapers following murders in Vallejo, San Francisco and other nearby towns in 1968 and 1969. The correspondence included cryptogram puzzles as clues to his identity and claimed he had killed as many as 37 people.

Two of letters were handed to a private lab by a Vallejo Police Department two months ago and the results are expected results soon.

“They were confident they would be able to get something off it,” Vallejo detective Terry Poyser told the Sacramento Bee.

Police in Vallejo, a city near to San Francisco, are leading the investigation into the Zodiac Killer – a name he used in his letters - because his first two victims were shot dead there.

Various pieces of evidence, including letters and a rope used to tie a victim, have previously been tested unsuccessfully for the killer’s DNA profile.

Vallejo mayor Bob Sampayan said samples were sent to the lab as a matter of routine every couple of years in hopes that advances in DNA testing will finally yield a profile detectives can use.

The former homicide detective said “it was coincidental” that the latest DNA test was taking place at the time of the breakthrough in the Golden State Killer case.

“There will come a time when we get a match,” Mr Sampayan added.

The 2007 film Zodiac, starring Jake Gyllenhaal and Robert Downey Jr, renewed widespread interest in a case that has always had a cult following of amateur detectives and cryptographers who sought to crack the killer’s code.

One of those amateur sleuths, Tom Voigt, said the key to solving the Zodiac killings was mimicking the Golden State Killer investigation, which included forming a full-time task force dedicated to the case and exploiting publicly accessible DNA databases.

He said the Zodiac case was being investigated part time by a Police Department in a city that filed for municipal bankruptcy.

“There’s a formula to follow,” Mr Voigt said. “And it’s to simply copy what happened to the Golden State Killer.”