The FBI announced a national campaign in 2016, offering a fifty-thousand-dollar reward for information leading to the identification of the Golden State Killer, and publicizing the case with updated information about the physical description of the suspect as he would have appeared at different ages. The campaign generated tips. Investigators tested DNA from some people identified through tips. Every tested individual was excluded.
The investigation had generated, over its decades, a situation familiar to cold-case investigators: substantial evidence, preserved DNA from multiple scenes, a behavioral profile, and an ever-narrowing suspect pool that had still not produced the person responsible. The DNA evidence was the most specific piece of evidence in the case — it was, theoretically, capable of identifying the exact person if that person’s DNA existed somewhere in a comparable database. But no comparable database had returned a match.
The criminal DNA databases — CODIS, the Combined DNA Index System maintained by the FBI — work by comparing crime-scene DNA against profiles submitted by convicted offenders and, in some states, people arrested for certain offenses. The Golden State Killer’s DNA had been in the CODIS system as an unidentified profile. No match had ever appeared. The person responsible had no prior criminal conviction that had placed his DNA in that system.
He was not in CODIS because he had never been convicted of a crime that required his DNA to be submitted. The forty-plus years since his crimes had passed without his being arrested, charged, or convicted of anything that would have placed him in the database.