1. Preserved Crime Scene Evidence:
Investigators had diligently collected and preserved physical evidence, including semen samples, from the crime scenes of the Golden Sate Killer attacks. Although DNA profiling was not widely available at the time, these samples were stored for potential future use.
2. Advances in DNA Profiling:
As DNA profiling technology advanced, it became possible to extract DNA even from old and degraded samples. In the early 2000s, law enforcement agencies began re-examining evidence from unsolved cases, including those linked to the Golden State Killer.
3. DNA Database Expansion:
Over the years, the state of California expanded its DNA database to include convicted offenders and arrestees. As the database grew, it increased the chances of finding matches with crime scene DNA.
4. Familial DNA Search:
In 2018, investigators used a novel technique called familial DNA search. They uploaded the Golden State Killer's DNA profile to the database and searched for close matches that might indicate a family relation.
5. Joseph DeAngelo's Son's DNA:
The familial search led to a partial match with the DNA of Joseph James DeAngelo's son, who had previously provided a sample during a traffic stop. This crucial connection narrowed down the investigation to Joseph DeAngelo himself.
6. Surveillance and DNA Collection:
Law enforcement discreetly placed DeAngelo under surveillance and eventually obtained a surreptitious DNA sample by collecting his discarded items, such as tissues and used toothbrushes.
7. DNA Profile Match:
DeAngelo's DNA profile matched the Golden State Killer's crime scene DNA, confirming that he was the elusive serial offender.
8. Arrest and Conviction:
Armed with the DNA evidence, law enforcement authorities arrested Joseph James DeAngelo in April 2018 at the age of 72, bringing an end to the decades-long manhunt for the Golden State Killer.
DeAngelo's DNA evidence was instrumental in connecting him to multiple homicides, rapes, and burglaries committed across California. His conviction and sentencing brought justice to the surviving victims and closure to the families affected by the horrifying crimes committed by the Golden State Killer.
