The Associated Press reports that detectives in Northern California are trying to find a break in the famous Zodiac Killer cases from the 1960s by attempting to test for DNA on envelopes he may have licked before sending letters to investigators. This announcement comes days after the same methods were used to track down the Golden State Killer.

Police are trying to extract a better DNA profile with updated technology that wasn’t available just a few short years ago. They are hoping to utilize public DNA profiles, much like they did with the Golden State Killer cases, in order to identify a suspect.

The Zodiac Killer is blamed for fatally stabbing or shooting five people in Northern California in 1968 and 1969. He then sent a series of taunting letters to detectives, who were unable to determine his identity. The killer was named the “Zodiac” because of his use of cryptograms that contained astrological references and symbols.

Other pieces of evidence, including a rope used to tie up a victim and the letters have been tested in the past with no luck. The Vallejo Police Department sent two of the letters written by the killer several months ago to a lab, hoping to find his DNA on the stamps or envelope flaps. Results are expected to be announced soon.

*Photo credit Associated Press