• Ski masks believed used by the East Area Rapist are part of the FBI’s evidence. Photo: FBI
Photo: FBI
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Ski masks believed used by the East Area Rapist are part of the FBI’s evidence.
Ski masks believed used by the East Area Rapist are part of the FBI’s evidence.
Photo: FBI
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FBI Special Agent Marcus Knutson and Sacramento County Sheriff’s Department Deputy Paige Kneeland work on the East Area Rapist case in the Sheriff’s Department evidence room.
FBI Special Agent Marcus Knutson and Sacramento County Sheriff’s Department Deputy Paige Kneeland work on the East Area Rapist case in the Sheriff’s Department evidence room.
Photo: FBI
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Joseph James DeAngelo has been arrested in rapes and killings dating to the 1970s.
Joseph James DeAngelo has been arrested in rapes and killings dating to the 1970s.
Photo: Sacramento County Sheriff’s Office
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Police arrested Joseph James DeAngelo, 72, in connection with crimes attributed to the East Area Rapist, over 30 years since he allegedly committed 12 murders and 45 rapes from 1976 to 1986.

Police arrested Joseph James DeAngelo, 72, in connection with crimes attributed to the East Area Rapist, over 30 years since he allegedly committed 12 murders and 45 rapes from 1976 to 1986.

Photo: Sacramento Sheriff’s Department
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Joseph DeAngelo has been charged in the 1978 murders of Brian Maggiore and wife Katie Maggiore, shown above. DeAngelo is suspected of being the "East Area Rapist," also known as the "Golden State Killer."

Joseph DeAngelo has been charged in the 1978 murders of Brian Maggiore and wife Katie Maggiore, shown above. DeAngelo is suspected of being the "East Area Rapist," also known as the "Golden State Killer."

Photo: Courtesy FBI
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Law enforcement authorities process evidence at the home of suspected "East Area Rapist" Joseph James DeAngelo, 72, in Citrus Heights, Calif., on Wednesday, April 25, 2018. (Randall Benton/Sacramento Bee/TNS)
Law enforcement authorities process evidence at the home of suspected "East Area Rapist" Joseph James DeAngelo, 72, in Citrus Heights, Calif., on Wednesday, April 25, 2018. (Randall Benton/Sacramento Bee/TNS)
Photo: Randall Benton, TNS
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FBI investigators stand in front of the home of accused rapist and killer Joseph James DeAngelo on April 24, 2018 in Citrus Heights, California. Sacramento District Attorney Anne Marie Schubert was joined by law enforcement officials from across California to announce the arrest of 72 year-old Joseph James DeAngelo who is believed to be the the East Area Rapist, also known as the Golden State Killer, who killed at least 12, raped over 45 people and burglarized hundreds of homes throughout California in the 1970s and 1980s. less
FBI investigators stand in front of the home of accused rapist and killer Joseph James DeAngelo on April 24, 2018 in Citrus Heights, California. Sacramento District Attorney Anne Marie Schubert was joined by ... more
Photo: Justin Sullivan, Getty Images
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A view of the home of accused rapist and killer Joseph James DeAngelo on April 24, 2018 in Citrus Heights, California. Sacramento District Attorney Anne Marie Schubert was joined by law enforcement officials from across California to announce the arrest of 72 year-old Joseph James DeAngelo who is believed to be the the East Area Rapist, also known as the Golden State Killer, who killed at least 12, raped over 45 people and burglarized hundreds of homes throughout California in the 1970s and 1980s. less
A view of the home of accused rapist and killer Joseph James DeAngelo on April 24, 2018 in Citrus Heights, California. Sacramento District Attorney Anne Marie Schubert was joined by law enforcement officials ... more
Photo: Justin Sullivan, Getty Images
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An FBI investigator enters the home of accused rapist and killer Joseph James DeAngelo on April 24, 2018 in Citrus Heights, California. Sacramento District Attorney Anne Marie Schubert was joined by law enforcement officials from across California to announce the arrest of 72 year-old Joseph James DeAngelo who is believed to be the the East Area Rapist, also known as the Golden State Killer, who killed at least 12, raped over 45 people and burglarized hundreds of homes throughout California in the 1970s and 1980s. less
An FBI investigator enters the home of accused rapist and killer Joseph James DeAngelo on April 24, 2018 in Citrus Heights, California. Sacramento District Attorney Anne Marie Schubert was joined by law ... more
Photo: Justin Sullivan, Getty Images
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A photo of accused rapist and killer Joseph James DeAngelo is displayed during a news conference on April 25, 2018 in Sacramento, California. Sacramento district attorney Anne Marie Schubert was joined by law enforcement officials from across California to announce the arrest of 72 year-old Joseph James DeAngelo who is believed to be the the East Area Rapist, also known as the Golden State Killer, who killed at least 12, raped over 45 people and burglarized hundreds of homes throughout California in the 1970s and 1980s. less
A photo of accused rapist and killer Joseph James DeAngelo is displayed during a news conference on April 25, 2018 in Sacramento, California. Sacramento district attorney Anne Marie Schubert was joined by law ... more
Photo: Justin Sullivan / Getty Images
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In an undated photo released by the FBI, documents related to the decades-long investigation into a serial killer and rapist, known variously as the Golden State Killer, the East Area Rapist or the Original Night Stalker, who terrorized California in the 1970s and 1980s. Joseph James DeAngelo was reportedly arrested and charged with two counts of murder in relation to the case on April 25, 2018. (Federal Bureau of Investigation via The New York Times) -- FOR EDITORIAL USE ONLY -- less
In an undated photo released by the FBI, documents related to the decades-long investigation into a serial killer and rapist, known variously as the Golden State Killer, the East Area Rapist or the Original ... more
Photo: FEDERAL BUREAU OF INVESTIGATION;Federal Bureau Of Investigation / New York Times
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An FBI photo showing evidence at the scene of one of the East Area Rapist’s attacks. Joseph James DeAngelo, 72, was arrested in connection with the case on April 25, 2018.

An FBI photo showing evidence at the scene of one of the East Area Rapist’s attacks. Joseph James DeAngelo, 72, was arrested in connection with the case on April 25, 2018.

Photo: Courtesy FBI
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An FBI photo showing evidence at the scene of one of the East Area Rapist’s attacks. Joseph James DeAngelo, 72, was arrested in connection with the case on April 25, 2018.

An FBI photo showing evidence at the scene of one of the East Area Rapist’s attacks. Joseph James DeAngelo, 72, was arrested in connection with the case on April 25, 2018.

Photo: Courtesy FBI
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A ring stolen by the East Area Rapist from one of his victims. He was known for taking items of sentimental, rather than monetary, value. Joseph James DeAngelo, 72, was arrested in connection with the case on April 25, 2018.

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A ring stolen by the East Area Rapist from one of his victims. He was known for taking items of sentimental, rather than monetary, value. Joseph James DeAngelo, 72, was arrested in connection with the case on

... more
Photo: Courtesy FBI
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The East Area Rapist often wore ski masks like the ones shown here in evidence at the Sacramento County Sheriff’s Department. Joseph James DeAngelo, 72, was arrested in connection with the case on April 25, 2018.

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The East Area Rapist often wore ski masks like the ones shown here in evidence at the Sacramento County Sheriff’s Department. Joseph James DeAngelo, 72, was arrested in connection with the case on April 25,

... more
Photo: Courtesy FBI
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A poster marking the locations of crimes committed by the East Area Rapist, also known as the Golden State Killer, sits on display during a news conference at the Sacramento County Sheriff's Department in Sacramento, California, on Wednesday, June 15, 2016. less
A poster marking the locations of crimes committed by the East Area Rapist, also known as the Golden State Killer, sits on display during a news conference at the Sacramento County Sheriff's Department in ... more
Photo: Connor Radnovich / The Chronicle
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The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged with murder in one off the cases and is suspected to have killed up many more.

less

The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged

... more
Photo: FBI
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The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged with murder in one off the cases and is suspected to have killed up many more.

less

The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged

... more
Photo: FBI
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The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged with murder in one off the cases and is suspected to have killed up many more.

less

The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged

... more
Photo: FBI
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The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged with murder in one off the cases and is suspected to have killed up many more.

less

The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged

... more
Photo: FBI
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The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged with murder in one off the cases and is suspected to have killed up many more.

less

The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged

... more
Photo: FBI
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The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged with murder in one off the cases and is suspected to have killed up many more.

less

The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged

... more
Photo: FBI
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The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged with murder in one off the cases and is suspected to have killed up many more.

less

The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged

... more
Photo: FBI
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The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged with murder in one off the cases and is suspected to have killed up many more.

less

The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged

... more
Photo: FBI
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The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged with murder in one off the cases and is suspected to have killed up many more.

less

The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged

... more
Photo: FBI
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The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged with murder in one off the cases and is suspected to have killed up many more.

less

The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged

... more
Photo: FBI
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The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged with murder in one off the cases and is suspected to have killed up many more.

less

The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged

... more
Photo: FBI
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Sgt. Paul Belli of the Sacramento County Sheriff's Department gestures toward sketches while speaking to the media at a news conference at the sheriff's department in Sacramento, California, on Wednesday, June 15, 2016. Law enforcement agencies announced a national campaign to identify and apprehend the East Area Rapist, also known as the Golden State Killer, who committed his first crime 40 years ago. less
Sgt. Paul Belli of the Sacramento County Sheriff's Department gestures toward sketches while speaking to the media at a news conference at the sheriff's department in Sacramento, California, on Wednesday, June ... more
Photo: Connor Radnovich, The Chronicle
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Sketches of the East Area Rapist, also known as the Golden State Killer, sit on display during a news conference at the Sacramento County Sheriff's Department in Sacramento, California, on Wednesday, June 15, 2016. less
Sketches of the East Area Rapist, also known as the Golden State Killer, sit on display during a news conference at the Sacramento County Sheriff's Department in Sacramento, California, on Wednesday, June 15, ... more
Photo: Connor Radnovich / The Chronicle
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A sketch of the East Area Rapist, also known as the Golden State Killer, sit on display during a news conference at the Sacramento County Sheriff's Department in Sacramento, California, on Wednesday, June 15, 2016.

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A sketch of the East Area Rapist, also known as the Golden State Killer, sit on display during a news conference at the Sacramento County Sheriff's Department in Sacramento, California, on Wednesday, June 15,

... more
Photo: Connor Radnovich / The Chronicle
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Photo: Courtesy FBI
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This FBI wanted poster obtained April 25, 2018 shows drawings of a suspect known as the "Golden State Killer". A notorious decades-old mystery over the identity of the "Golden State Killer," believed to have carried out dozens of rapes and multiple murders in California in the 1970s and 1980s, may finally be solved: a suspect has reportedly been arrested. Joseph James DeAngelo, 72, is being held in the Sacramento County jail on two counts of murder, the Sacramento Bee reported on April 25, 2018.According to local television stations, DeAngelo was once a policeman. The Golden State Killer, also known as the "East Area Rapist" and "Original Nightstalker," is suspected of carrying out at least 12 murders and 45 rapes in California between 1976 and 1986, according to the FBI. / AFP PHOTO / FBI / Handout / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / FBI/HANDOUT" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS HANDOUT/AFP/Getty Images less
This FBI wanted poster obtained April 25, 2018 shows drawings of a suspect known as the "Golden State Killer". A notorious decades-old mystery over the identity of the "Golden State Killer," believed to have ... more
Photo: HANDOUT;Handout / AFP / Getty Images
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On February 2, 1978, Brian Maggiore and his wife, Katie, were on an evening walk with their dog in their Rancho Cordova neighborhood in California when they were chased down and murdered by the East Area Rapist. less
On February 2, 1978, Brian Maggiore and his wife, Katie, were on an evening walk with their dog in their Rancho Cordova neighborhood in California when they were chased down and murdered by the East Area ... more
Photo: / Courtesy FBI
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A ring stolen by the East Area Rapist from one of his victims. He was known for taking items of sentimental, rather than monetary, value. Joseph James DeAngelo, 72, was arrested in connection with the case on April 25, 2018.

less

A ring stolen by the East Area Rapist from one of his victims. He was known for taking items of sentimental, rather than monetary, value. Joseph James DeAngelo, 72, was arrested in connection with the case on

... more
Photo: Courtesy FBI
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An FBI photo showing evidence at the scene of one of the East Area Rapist’s attacks. Joseph James DeAngelo, 72, was arrested in connection with the case on April 25, 2018.

An FBI photo showing evidence at the scene of one of the East Area Rapist’s attacks. Joseph James DeAngelo, 72, was arrested in connection with the case on April 25, 2018.

Photo: Courtesy FBI
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An FBI photo showing evidence at the scene of one of the East Area Rapist’s attacks. Joseph James DeAngelo, 72, was arrested in connection with the case on April 25, 2018.

An FBI photo showing evidence at the scene of one of the East Area Rapist’s attacks. Joseph James DeAngelo, 72, was arrested in connection with the case on April 25, 2018.

Photo: Courtesy FBI
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The East Area Rapist often wore ski masks like the ones shown here in evidence at the Sacramento County Sheriff’s Department. Joseph James DeAngelo, 72, was arrested in connection with the case on April 25, 2018.

less

The East Area Rapist often wore ski masks like the ones shown here in evidence at the Sacramento County Sheriff’s Department. Joseph James DeAngelo, 72, was arrested in connection with the case on April 25,

... more
Photo: Courtesy FBI
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In this undated photo released by the FBI shows a East Area Rapist Fence in Sacramento, Calif. The levee behind this fence led to areas of thick brush and the American River, which the subject often used to make his escape. A California sheriff says a former police officer accused of being a serial killer and rapist was taken by surprise when deputies swooped in and arrested him as he stepped out of his home. Sacramento County Sheriff Matt Jones said deputies planned to arrest Joseph DeAngelo when he left his home on Tuesday, April 24, 2018. (FBI via AP) less
In this undated photo released by the FBI shows a East Area Rapist Fence in Sacramento, Calif. The levee behind this fence led to areas of thick brush and the American River, which the subject often used to ... more
Photo: Associated Press
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The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged with murder in one off the cases and is suspected to have killed up many more.

less

The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged

... more
Photo: FBI
Image 49 of 62

The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged with murder in one off the cases and is suspected to have killed up many more.

less

The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged

... more
Photo: FBI
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The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged with murder in one off the cases and is suspected to have killed up many more.

less

The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged

... more
Photo: FBI
Image 52 of 62

The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged with murder in one off the cases and is suspected to have killed up many more.

less

The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged

... more
Photo: FBI
Image 53 of 62

The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged with murder in one off the cases and is suspected to have killed up many more.

less

The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged

... more
Photo: FBI
Image 54 of 62

The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged with murder in one off the cases and is suspected to have killed up many more.

less

The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged

... more
Photo: FBI
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The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged with murder in one off the cases and is suspected to have killed up many more.

less

The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged

... more
Photo: FBI
Image 57 of 62

The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged with murder in one off the cases and is suspected to have killed up many more.

less

The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged

... more
Photo: FBI
Image 58 of 62

The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged with murder in one off the cases and is suspected to have killed up many more.

less

The FBI has released these evidence photos from crimes suspected to have been commited by the East Area Rapist, also known as the Golden State Killer. Citrus Heights residents Joesph DeAngelo has been charged

... more
Photo: FBI
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In this undated photo released by the FBI shows Sacramento County Sheriff's Department Deputy Paige Kneeland searching for evidence in the East Area Rapist case at the Sheriff's department evidence room in Sacramento, Calif. Here, Sacramento County Sheriff's Department Deputy Paige Kneeland sorts through reams of evidence in the East Area Rapist case. A California sheriff says a former police officer accused of being a serial killer and rapist was taken by surprise when deputies swooped in and arrested him as he stepped out of his home. Sacramento County Sheriff Matt Jones said deputies planned to arrest Joseph DeAngelo when he left his home on Tuesday, April 24, 2018. (FBI via AP) less
In this undated photo released by the FBI shows Sacramento County Sheriff's Department Deputy Paige Kneeland searching for evidence in the East Area Rapist case at the Sheriff's department evidence room in ... more
Photo: Associated Press
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This undated photo released by the FBI shows part of East Area Rapist Crime reports at the Sheriff's department evidence room in Sacramento, Calif. Volumes of reports about the murder investigation are contained in the evidence room at the Sacramento County Sheriff's Department. A California sheriff said Joseph James DeAngelo, a former police officer accused of being a serial killer and rapist, was taken by surprise when deputies swooped in and arrested him Tuesday, April 24, 2018, as he stepped out of his home. (FBI via AP) less
This undated photo released by the FBI shows part of East Area Rapist Crime reports at the Sheriff's department evidence room in Sacramento, Calif. Volumes of reports about the murder investigation are ... more
Photo: Associated Press
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SACRAMENTO — Investigators broke open the long-stagnant case of the prolific serial killer and rapist known as the Golden State Killer by mining DNA profiles collected by a genealogical website used by individuals to trace family heritage, sources told The Chronicle on Thursday.

Law enforcement had long had a DNA profile of the suspected killer, which helped them connect murders and rapes across the state to the same unidentified man. But, the DNA profile did not match any contained in criminal databases that are used by law enforcement throughout the U.S. to link crimes to suspects.

The explosion in recent years of DNA heritage websites such as 23andMe and Ancestry.com provided investigators with another tool, although both of those companies said Thursday they were not involved in this case. The genealogical site, which was not revealed, linked the suspect’s DNA profile to a likely family member, the sources said. They also obtained a court order to compel the site to work with them.

That narrowed their search, and ultimately detectives got what they had long waited for — a DNA match — to Joseph James DeAngelo after following him and collecting an item he had discarded that they say contained his DNA.

DNA experts said the use of genealogical websites is a controversial and unorthodox method to solving crimes, one that could pose some ethical questions if it involves a commercial company where users have an expectation of privacy.

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The arrest of Joseph DeAngelo in connection with the East Area Rapist and Golden State Killer cases.

Media: San Francisco Chronicle

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There are also publicly available databases online where anyone can upload and view DNA results in order to learn more about their family tree.

Investigators have been hesitant to reveal how they came to identify DeAngelo as the suspect known as the Golden State Killer or East Area Rapist, whose reign of terror included 12 slayings and 45 rapes in California from 1976 to 1986. DeAngelo had never been on their radar previously.

Sacramento Sheriff Scott Jones said a task force trying to solve the heinous crimes turned to “very innovative and emerging DNA technology that gave us a universe to look in.”

Jones added that it was not a tip that led them to DeAngelo’s perfectly manicured Citrus Heights home in Sacramento County.

It’s possible, said New York University Law Professor Erin Murphy, an expert in forensic evidence, that detectives might be reluctant to tell the public how they identified a suspect because they know people are uneasy about the use of genealogy websites as crime-fighting tools. If a commercial company turned over DNA information, Murphy said that would not be unprecedented, but also not without problems.

“There could be huge ethical issues there,” Murphy said.

One of the biggest genealogical companies, Ancestry.com, said the company has had no contact with law enforcement in the DeAngelo case. The company’s policy is to only provide information when compelled by court order or warrant, a spokeswoman said.

The company has received one search warrant in its history demanding that it identify a person based on a DNA sample. In that 2014 case, police searched a public DNA database owned by Ancestry.com using DNA collected at a homicide scene in Idaho and found a profile that matched 35 of 36 genetic markers, leading to the possibility that a family member of that person was their suspect. While the DNA profile was public, the name of the person who uploaded it was not, leading police to get a warrant for the identity.

In that case, police hit another dead end, ultimately clearing a man they suspected of any wrongdoing and saying that his family members were also not involved.

A spokesman from 23andMe, a genetic testing firm based in Mountain View, said the company was also not contacted in the DeAngelo case.

It’s possible, Murphy said, that detectives used various public genealogy websites, which she said eases privacy or ethical questions.

Detectives could have focused on the Y-STR — part of the male Y chromosome that is handed down paternally — to find a relative or find a likely last name, Murphy said. Combine that narrowed list with the likely age of a suspect and geography, and “that could give you a smaller list of names,” Murphy said.

The use of a genealogical site is different than a traditional familial searches using DNA — like the one that unmasked the Grim Sleeper. In the case of the Grim Sleeper, police linked Lonnie Franklin Jr. to the killings of 10 people over 25 years using a DNA sample from his son, whose genetic profile had been uploaded into a database of known criminals.

“The familial search process, the way it’s designed and the way it works, it gives you a father, son or full sibling,” said Rockne Harmon, a consultant to numerous law enforcement agencies on cold cases and former Alameda County prosecutor.

That’s not the process law enforcement were describing when they unmasked their suspect Wednesday at a news conference outside the Sacramento district attorney’s crime lab. There, they described a flurry of activity over the past week as it appeared they were closing in on one suspect.

DeAngelo’s name was known to investigators at least a month ago. Paul Holes, a Contra Costa County cold case investigator, said the list of potential suspects had been narrowed to a handful of men, roughly five — DeAngelo among them. Still, DeAngelo wasn’t at the top of that list, Holes said, until DNA ruled out some of the other men.

Sacramento’s sheriff’s began surveilling DeAngelo’s home and were able to obtain two “surreptitious samples” from him — meaning they waited for him to discard something with his DNA on it.

Investigators got one sample a week before his arrest. It was too weak, Holes said. They went back and tested a second sample they got Monday, which investigators said was a 100 percent match. DeAngelo was arrested that evening. It was the peak of a roller coaster that started for Holes in the 1990s, when he looked into the cold case during DNA’s infancy.

Like with Holes, the case had long clung to those who tried to identify the suspect.

“It’s been a very frustrating. You have your moments of highs thinking you got the guy, and then you crash when the DNA evidence eliminates him,” Holes said. “The frustration just builds. To finally get to the point where you find the right guy, it is a very good feeling.”

Demian Bulwa, Melody Gutierrez and Jenna Lyons are San Francisco Chronicle staff writers. Email: dbulwa@sfchronicle.com, mgutierrez@sfchronicle.com, jlyons@sfchronicle.com Twitter: @demianbulwa, @MelodyGutierrez, @JennaJourno