Detectives had searched for four decades for the clue that would unlock the identity of the Golden State Killer, the predator who terrorized California top to bottom with a string of horrific rapes and homicides in the 1970s and \u201980s.\r\nCriminal DNA databases produced no hits, sweeps of crime scenes no fingerprints and hefty rewards no definitive tips. But Paul Holes, an investigator and DNA expert, had a hunch he could create a road map to the killer through his genetics.\r\nHoles used DNA recovered from a crime scene to find the killer\u2019s great-great-great grandparents, who lived in the early 1800s. Branch by painstaking branch, he and a team created about 25 family trees containing thousands of relatives down to the present day.\r\nOne fork led to a 72-year-old retiree who was quietly living out his golden years in the Sacramento suburb of Citrus Heights. Holes was intrigued after learning the man was a disgraced cop who had bought guns during two bursts of activity by the killer.\r\nThe test of Holes\u2019s novel sleuthing would come in mid-April, when officers scooped up an item discarded by the man that contained his DNA and tested the genetic material against the killer\u2019s. The shot in the dark produced a match \u2014 an improbable ending fit for detective fiction.\r\nJoseph James DeAngelo\u00a0was arrested\u00a0in Citrus Heights on April\u00a024.\r\n\r\n\u201cEverything else up to this time had failed,\u201d Holes said. \u201cFor 44 years, law enforcement has been trying to solve this case. No other case has had more resources poured into it in the history of California. I was just stunned.\u201d\r\nThe role of genetics in the case is well known, but this account reveals for the first time the massive scope, intricate science and sheer doggedness of the effort to catch one of the nation\u2019s worst serial predators.\r\nInitial DNA work identified distant relatives \u2014 not a suspect. Holes said a team of five investigators spent four months building out family trees, name by name. They pored over census records, newspaper obituaries, gravesite locaters, and police and commercial databases to find each relative and, ultimately, DeAngelo.\r\n\r\nThe Golden State Killer was as clever a criminal as he was sadistic, taunting authorities and staying one step ahead as police say he killed at least 12 people, raped more than 50 and committed 100 burglaries between 1974 and 1986, when his crimes appeared to mysteriously end.\r\nHis mayhem touched 10 counties, and he was variously called the East Area Rapist, Original Nightstalker, Diamond Knot Killer and Visalia Ransacker before authorities discovered that the various strings of crimes appeared to be the work of a single man.\r\nHe instilled fear like few others.\r\nSacramento District Attorney Anne Marie Schubert was a child when dozens of seemingly related rapes occurred in the Sacramento area in 1976 and 1977. Schubert said her mother put a weapon under her pillow.\r\n\u201cIt changed this community,\u201d Schubert said. \u201cPeople referred to him as the boogeyman. It wasn\u2019t a matter of if he was coming, it was when, because it happened so much and it went on for so long.\u201d\r\nThe boogeyman\r\nThe horror began with the flash of a blinding light.\r\nLinda O\u2019Dell, then 22, said she and her husband were woken about 1 or 2\u00a0a.m. on May\u00a014, 1977, by an intruder shining a flashlight on their bed.\r\n\u201cDon\u2019t move,\u201d the man barked.\r\nHe threw string to O\u2019Dell and ordered her to tie up her husband. Then the intruder tied O\u2019Dell up himself. He piled plates and bowls on her husband\u2019s back and stalked around the house yelling and drinking the couple\u2019s beer. Finally, he moved O\u2019Dell to the living room, where he raped her.\r\n\u201cHe told me he would cut my husband\u2019s ear off and bring it to me if there was any noise,\u201d she said.\r\nHe eventually took O\u2019Dell\u2019s wedding ring, possibly as a souvenir, then slipped out into the night.\r\nThe three-hour ordeal bore the terrible hallmarks of a predator who came to be dubbed the East Area Rapist. The rape of O\u2019Dell was No.\u00a021 attributed to the same man in the Sacramento area in 1976 and 1977. Thirty more would follow there and in other communities in Northern California.\r\n\r\n\u201cThis was the most heinous rapist I had ever known,\u201d said former detective Carol Daly, who was one of the first to investigate the case for the Sacramento County Sheriff's Department. \u201cThe attacks were bizarre, cruel and long-lasting.\u201d\r\nThey were also cunning, said Richard Shelby, another former detective with the department. Shelby said the East Area Rapist planned meticulously. He watch\u00aded the victims, broke into their homes and even called them to learn their routines before striking. He always seemed to have an escape route via a stream, trail or field.\r\nWith each attack, fear ratcheted higher.\r\nSales of locks, dogs and guns soared \u2014 doubling in Sacramento County between 1976 and 1977, according to the Sacramento Bee. Daly said burglaries nose-dived during that era; she surmised it was because of the gun sales and burglars knowing that residents were on edge.\r\nBut what truly seemed to set the East Area Rapist apart, Daly said, was his apparent delight in stoking this public terror.\r\nAt a forum on the rapes in 1977, Daly recalled that a man rose and said he doubted a rapist would be able to rape a woman in front of her husband, since the man would retaliate. Several months later, that man\u2019s wife was raped while he was at home, Daly said.\r\n\u201cI can\u2019t positively say, but I think the rapist was in the meeting that night,\u201d she said.\r\nDespite intense searches, Shelby said, the East Side Rapist seemed to anticipate police moves and slip away. At the time, DeAngelo was a police officer in the small Northern California town of Auburn.\r\nIf DeAngelo is the East Side Rapist, Shelby thinks his police training may have given him an edge. His police radio may have even allowed him to listen in as police investigated.\r\nThe violence grew.\r\nIn February 1978, a young couple from Rancho Cordova, Brian and Katie Maggiore, were shot dead when they fled a confrontation on the street while walking their dog. The killings eventually became the first attributed to the East Area Rapist.\r\nThe year after the killings, DeAngelo was dismissed from the Auburn force for shoplifting a can of dog repellent and a hammer from a drugstore.\r\n\r\n\r\n\u00a0\r\nThe terror soon shifted to Southern California, although it\u2019s unclear what DeAngelo was doing or where he was living.\r\nShortly after Christmas in 1979, a surgeon and a psychologist were shot and killed in their Santa Barbara County apartment. In March 1980, a couple was fatally bludgeoned with a piece of firewood in their Ventura County home. The woman was raped. Six more homicides would follow, all believed to be the work of a killer who was dubbed the Original Nightstalker.\r\nBy 1986, that wave of crimes appeared to abruptly end.\r\nThe reason remains unknown, but Daly and Shelby think the killer may have grown too old to continue the physically demanding attacks and flights. In 2001, DNA evidence linked the East Area Rapist and Original Nightstalker cases.\r\nThe search for the Golden State Killer helped spur advances in criminal justice. The brother of one victim successfully lobbied to expand the collection of DNA from criminals in California, and the Sacramento Sheriff\u2019s Department added a dedicated sex-crimes unit.\r\nThe final push to find the killer would spawn one more investigative innovation.\r\nRoad map to a killer\r\nPaul Holes had been tracking the Golden State Killer for 24 years, but time was running out. He had nine months before he retired as an investigator for the Contra Costa County district attorney\u2019s office, and he desperately wanted to crack his biggest case.\r\nHoles had been obsessed with the Golden State Killer since coming across the case file in the mid-90s while working as a forensic scientist. Holes had handled serial predator cases, but the Golden State Killer stood out even among these hardened offenders.\r\n\u201cI was struck by the lengths this predator would go to to instill fear in his victims,\u201d Holes said. \u201cIt was psychological terror.\u201d\r\nA detective told Holes about a 2002 case in which a young kidnapping victim was identified using her DNA and a genealogy website. Holes wondered: Could he do the same with the Golden State Killer?\r\n\r\nHoles began researching and hit upon a novel tool in GEDmatch, a no-frills website that allows users to upload their genetic information and search a database of roughly 1\u00a0million profiles for possible family connections.\r\nHe prepared to sell the un\u00ad\u00ad\u00ad\u00ad\u00ad\u00ador\u00adtho\u00addox idea to officials to get a sample of the killer\u2019s DNA.\r\n\u201cWe ended up going on a road show,\u201d Holes said.\r\nHoles and an FBI lawyer found a partner in Ventura County last summer. A meticulous pathologist had put a duplicate evidence kit from the rape and murder of Charlene and Lyman Smith in a freezer in 1980. Many other DNA samples from the case had been depleted over the years.\r\n\r\nThis undated photo shows renderings produced during the investigations. (FBI\/AP)\r\nA lab converted the sample into a format that could be read by GEDmatch, which analyzes hundreds of thousands of DNA datapoints to determine relatedness. Holes waited anxiously as he fed in the killer\u2019s profile.\r\nHoles, prepared for another dead end, was heartened when the analysis returned. It wasn\u2019t a close match, but the site found 10 to 20 distant relatives of the killer, roughly the equivalent of third cousins.\r\nHoles knew that if he traced back the lineages of distant cousins far enough, he could find a common ancestor they shared with the killer. That turned out to be great-great-great grandparents from the early 1800s.\r\nA daunting task lay ahead as Holes and his team began to trace offspring to the present day to find potential suspects. That meant filling in thousands of blanks.\r\n\u201cWhen you go that far back in time, you have trees that grow huge,\u201d Holes said.\r\nThey used census data, old newspaper clippings and a gravesite locator to find the deceased relatives. When they got to the current day, they turned to police databases and websites such as LexisNexis.\r\nHoles created his family trees using a tool on Ancestry.com. His team stole time on weekends and during meetings to plug the holes one by one. It was tedious work, and it wasn\u2019t their full-time focus.\r\nBy April, they had pieced together about 25 distinct family trees from the great-great-great grandparents. There were roughly 1,000 family members just in the one that included DeAngelo.\r\nThe team began scouring the trees for potential suspects, men about the killer\u2019s age who had connections to Sacramento and other locations of the crimes.\r\n\r\nThey found two.\r\nHoles said the other suspect looked promising on paper but was eventually eliminated by a DNA test of a relative. That left DeAngelo.\r\nHoles had doubts.\r\n\u201cHow could this guy be a full-time law enforcement officer and be committing all these attacks across Northern California?\u201d he said. \u201cI had my reservations that it was him.\u201d\r\nSacramento sheriff\u2019s deputies put DeAngelo under surveillance and picked up the discarded item containing his DNA. After the match, they arrested DeAngelo at his home, not far from where he allegedly carried out many of the crimes. He now faces eight counts of murder.\r\nOn Friday, DeAngelo, whose attorney did not return calls seeking comment for this article, was pushed into a Sacramento courtroom in a wheelchair to face arraignment. He appeared frail in an orange jumpsuit, answering a judge's questions in a thin, raspy voice.\r\nHoles said he was gratified to finally put a face to the ghost he chased for so many years.\r\n\u201cThousands of nightmares and thousands of sleepless nights have been put to an end with the capture of this rapist,\u201d Carol Daly said.