IMAGES/AFP/File / JUSTIN SULLIVAN
The mugshot of accused 'Golden State Killer'
Joseph James DeAngelo on display at a
Sacramento press conference where his arrest
Detectives in California used DNA left at
crime scenes, combined with genetic
information from a relative who joined an
online genealogy service, to catch an
alleged rapist and murderer who eluded
authorities for four decades.
The arrest this week of 72-year-old Joseph
James DeAngelo -- believed to be the "Golden
State Killer" responsible for 12 murders and
more than 50 rapes in the 1970s and 1980s --
was hailed as a victory for cutting-edge
science and old-fashioned detective work.
"The answer was, and always was going to be,
in the DNA," said Sacramento County District
Attorney Anne Marie Schubert.
Here's how it unfolded.
- Crime scene DNA -
Schubert opened a cold case investigation
into the Golden State Killer two years ago,
according to The New York Times.
Investigators started with DNA samples from
crime scenes that were in storage to build a
genetic profile of the suspected attacker,
which they then uploaded into an online
genealogy database to see if they could find
A Lake Worth, Florida-based company called
GEDMatch acknowledged on Friday that its
database "was used to help identify the
Golden State Killer... although we were not
approached by law enforcement or anyone else
about this case or about the DNA."
The FBI wanted poster for the 'Golden State
The company warned customers in a
statement that even though the site was
intended for genealogical research, possible
uses of their DNA include "identification of
relatives that have committed crimes or were
victims of crimes," and that they should
delete their profiles if they had any
Although DeAngelo himself had not sent his
own DNA to GEDMatch, at least one distant
relative of his had done so, and possibly
GEDMatch is a website that "pools raw
genetic profiles that people share
publicly," Paul Holes, a retired district
attorney inspector, told the East Bay Times.
"No court order was needed to access that
site's large database of genetic
Larger companies including Ancestry.com and
23andMe denied any link to the investigation
and said they had not given any customer
data to law enforcement officials.
- Online family trees -
People who are related share chunks of
identical DNA, which is interspersed with
sections of different DNA.
Identifying these shared patterns can point
investigators to people who are distant or
close kin, depending on the extent of the
The crime lab began exploring online family
trees that appeared to mirror the suspect's
Then, they hunted for clues about various
individuals in those families, to see if
they were possible suspects.
On April 19, detectives decided that
DeAngelo might be the one because a number
of factors aligned: the DNA, his age, and
the fact that he lived in the area where the
Investigators set up surveillance in the
tree-lined suburb where DeAngelo lived.
Then, Schubert said, "abandoned" DNA samples
were acquired from him.
Officials have not said what was used, but
it could have been a soda can, a hairbrush,
or anything containing DeAngelo's saliva,
hair or blood.
"You leave your DNA in a place that is a
public domain," she said.
This allowed experts to compare the newly
collected sample to the old DNA from the
crime scene, and it was a match to more than
10 of the murders.
The sample provided "overwhelming evidence
that it was him," Schubert said, according
to the Sacramento Bee.
- 'Astronomical evidence' -
Schubert asked the sheriff's office to
collect a second sample, to be sure. So they
"The second sample was astronomical evidence
that it was him," she said.
DeAngelo was arrested outside his home
Tuesday and charged with murdering two
people in 1978 in Rancho Cordova,
He is expected to face more charges.
"This was a true convergence of emerging
technology and dogged determination by
detectives," Sacramento County Sheriff Scott