One afternoon in January of 2012, a Los Angeles dog walker named Lauren Kornberg was taking a stroll through Griffith Park with her mother and nine canines. They were wending their way through Bronson Canyon, a rocky area that sits downhill from the Hollywood sign, when all of a sudden a golden retriever named Ollie ran off the trail and began to dig excitedly under a bush.

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As soon as the dog retrieved what he was after — a heavy-looking object inside a plastic bag — he dropped it in alarm. Whatever was inside proceeded to roll about 30 feet down a hill and into a ravine. The first thought that crossed Kornberg’s mind was that it was a prop of some kind, since the scrubby terrain of Bronson Canyon has served as a backdrop for countless movie and TV shoots. Kornberg’s mother insisted on climbing down to find it. Only when they were right up close, about a foot away, did they get a good look at the head — eyes and eyelashes, salt-and-pepper hair, and blood smeared over its face.

Dozens of police officers combed the surrounding brush the next day. They found two feet and a hand right near where Ollie had found the head, then another hand about 200 yards away. They kept searching for a week and found nothing more. By then, they knew the remains were those of a 66-year-old retired airline ticketing agent and art collector named Hervey Medellin, who had been missing since late December.

The media jumped on the “Mystery of the Hollywood Head,” as one headline dubbed it. Theories floated that Mexican drug cartels had been involved; that an ex–porn star who was suspected in another murder-and-dismemberment case had gotten to Medellin; or that Medellin’s neighbor, a bodyguard for Brad Pitt, had done it. But police, for their part, zeroed in on the victim’s much younger, unemployed roommate, who told investigators he was Medellin’s boyfriend.

Gabriel Campos-Martinez — 35, unassuming, and dour, with a shock of black hair and an intense stare — had been living with Medellin for about six months, and everything about his story raised suspicion. He told police that Medellin woke up one December morning and said he was leaving for Mexico, and that was the last Campos-Martinez had seen of him. But police could find no evidence that Medellin had gone anywhere in the weeks before the gruesome discovery — no ticket purchases, no gas station visits on his credit card. They learned that someone had transferred Medellin’s Social Security direct-deposit to an account controlled by both Medellin and Campos-Martinez. The latter’s browser history showed searches for diamond and gold websites, which made the cops wonder whether he’d been trying to sell some of Medellin’s belongings. Then there was the article that Campos-Martinez had apparently viewed online on December 27 — the last day Medellin was seen alive — about the best way to dismember a human carcass.

All that evidence, however, was maddeningly circumstantial. A search of the Hollywood apartment the two men had shared turned up very little: no murder weapon, no incriminating physical evidence. Their interrogations didn’t yield much either. In all, detectives questioned Campos-Martinez three times, but he had a gift for deflection. He claimed that Medellin had asked him to make those changes to the Social Security payments. And the web searches? “He just said that wasn’t him,” says detective Lisa Sanchez, one of the lead investigators. (There was no way to prove otherwise.)

To justify charging Campos-Martinez with murder, detectives knew they’d need more — if not a confession, at least more statements that contradicted the facts of the case. But Campos-Martinez was very good at feigning ignorance.

After weeks of investigation, the police asked Campos-Martinez to stay in touch and let them know his whereabouts. Shortly thereafter he told them he was moving to San Antonio, Texas. He started a new life. He found work as a waiter at the local convention center. He even got married — to a woman who, it seemed, had no idea he’d recently been in a relationship with a man, much less a man who’d been murdered and dismembered. Two years passed.

Then, one day, Campos-Martinez got a phone call from detective Chuck Knolls, Sanchez’s partner on the investigation. Medellin’s murder was a cold case now, he said, and two other detectives from the Robbery-Homicide Division, Greg Stearns and Tim Marcia, had been asked to look at it with fresh eyes. The pair would be passing through San Antonio on their way to look into cases elsewhere, he said, and he wanted to know if Campos-Martinez could meet the two of them and just talk. He was polite, respectful. He suggested meeting at the detectives’ hotel, near the Alamo. “We want to allow you to educate them,” he said.

The Medellin murder case had, by then, long since fallen off the radar of the Los Angeles media. But it was still closely watched inside the LAPD — and not just because the homicide investigation team was irked that their prime suspect had slipped away. To the department’s detectives, something bigger than Campos-Martinez was under close scrutiny in this case: the American way of interrogation.

The modern style of questioning criminal suspects — the set of techniques practiced fruitlessly by those first detectives in the Medellin case, and familiar to all of us from a thousand police procedurals — is a rusty, stalwart invention that’s been around since the days of JFK. It has a proud history: Born during a period of reform, it started out as an enlightened alternative to the bad old ways of policing that preceded it.

Until the mid-1930s, police still widely used the “third degree” — that is, torture — to get suspects to talk. Officers across the country hung suspects out of windows, dunked their heads underwater, and hit them. In 1931 a presidential panel known as the Wickersham Commission called attention to the brutality of the third degree. Then, in 1936, the US Supreme Court effectively outlawed the practice with its ruling in Brown v. Mississippi, a case involving three black men who were beaten and whipped until they confessed.

Police closed ranks at first, but they eventually came around to new approaches. J. Edgar Hoover, for one, was especially keen to rebrand his agents as advanced practitioners of law enforcement science. “Third-degree methods, an ill-trained officer might think, perhaps a severe beating, will force a confession,” Hoover said at the time. “But the trained officer, schooled in the latest techniques of crime detection, will think otherwise.” Crime labs were developing new methods of solving cases — ballistics, fingerprinting, document examination — and with them came a new, more psychological approach to interrogation.

The most influential nonviolent method of questioning suspects debuted in 1962 with the first edition of "Criminal Interrogation and Confessions," by Fred Inbau, a Northwestern University law professor who ran one of the country’s first crime labs, and John E. Reid, a former police officer turned polygraphy expert. Now in its fifth printing, the book set the mold for police interrogations in America. Through the 1940s and ’50s, Reid had built a reputation as a master interrogator, extracting confessions in over 300 murder cases. He and Inbau liken the interrogator’s task to “a hunter stalking his game.” An interrogation, they explained, should be designed to persuade a suspect that confessing is the only sensible option; to get confessions, they wrote, police must sweep up suspects in a wave of momentum that they’ll find impossible to reverse.

All the major tropes of a traditional police interrogation can be traced back to Reid and Inbau’s manual: the claustrophobic room, the interrogators’ outward projection of certainty, the insistence on a theory of the case that assumes the suspect’s guilt. (The manual calls this a “theme.”) The interrogators bolster that theme with what they characterize as incontrovertible evidence, which can include facts drawn from real detective work (“We know you got off work at 5 pm”) or details that are completely fabricated (“The polygraph says you did it”). Toward the end, interrogators are encouraged to “minimize” the crime in a consoling sort of way (“He had it coming, didn’t he?”). All the while, they cut off all denials until the suspect cracks. Detectives are allowed to use deceit and trickery because, as Inbau and Reid explained, none of these techniques are “apt to induce an innocent person to confess a crime he did not commit.”

The manual gave rise to a new archetype: the silver-tongued interrogator — someone who, through intimidation and seduction, can get anyone to admit to anything. No less an authority than the US Supreme Court acknowledged the sway that the method held over suspects; in its 1966 Miranda decision, the court cited the Inbau-Reid training manual as an example of why all suspects should be read their rights.

Over the years, the Reid technique, as it came to be known, became a kind of powerful folk wisdom, internalized by generations of police officers. Even among those who received little formal training, it was passed down from cop to cop. “You would think that at a large organization like the LAPD, a large emphasis would be put on developing interrogation skills for their detectives,” says Tim Marcia, reflecting on his own haphazard indoctrination into modern interrogation technique. “To be quite honest, we go to an 80-hour detective school, and probably about four hours is devoted to interrogation.”

Earlier in his career, Marcia spent 10 years as one of the original members of the LAPD’s cold-case unit. Researching old unsolved cases gave him a flyover view of interrogation tactics through the decades. While styles fluctuated somewhat, the basic outline of the Reid technique remained intact. And the most consistent thing over the years? No matter what detectives did with a suspect in the interrogation room, they were convinced they were doing it right.

The more confident police are about their judgment of a suspect's behavior, the more likely they are to be wrong.

The trouble with modern interrogation technique, as Marcia would learn, is that, despite its scientific pose, it has almost no science to back it up. Reid and Inbau claimed, for instance, that a well-trained investigator could catch suspects lying with 85 percent accuracy; their manual instructs detectives to conduct an initial, nonaccusatory “behavioral analysis interview,” in which they should look for physical tells like fidgeting and broken eye contact. But when German forensic psychologist Günter Köhnken actually studied the matter in 1987, he found that trained police officers were no better than the average person at detecting lies. Several subsequent studies have cast doubt on the notion that there are any clear-cut behavioral tells. (Truth tellers often fidget more than liars.) In fact, the more confident police officers are about their judgments, the more likely they are to be wrong.

But the scientific case against police interrogations really began to mount in the early 1990s, when the first DNA-based exonerations started rolling in. According to the Innocence Project, a group dedicated to freeing the wrongfully imprisoned, about a third of the 337 people who’ve had their convictions overturned by DNA evidence confessed or incriminated themselves falsely. These and other exonerations furnished scientists with dozens of known false-confession cases to study, giving rise to a veritable subfield of social psychology and the behavioral sciences. (At least one confession elicited by John Reid himself — in a 1955 murder case — turned out to be inaccurate; the real killer confessed 23 years later.)

Researchers have even broken down these false confession cases into categories. There are “voluntary” false confessions, like the many presumably unstable people who claimed credit for the Lindbergh baby kidnapping in order to get attention. Then there are “compliant,” or “coerced,” false confessions, in which people are so ground down by an intense interrogation that, out of desperation and naïveté, they think that confessing will be better for them in the long run. The third category, “persuaded,” or “internalized,” false confessions, may be the most poignant. Here, the interrogator’s Reid-style theming is so relentless, the deployment of lies so persuasive, that suspects — often young and impressionable or mentally impaired — end up believing they did it, however fleetingly.

And yet, even in the face of these documented cases, police and prosecutors have resisted admitting that false confessions are even possible. In court, they routinely move to reject expert testimony on the phenomenon by saying it goes against common sense that an innocent person would ever confess to a criminal act. But a wealth of research since the 1990s has shown that false memories are remarkably easy to implant. And in 2015, Julia Shaw, then a psychology PhD candidate in British Columbia, conducted a study that took direct aim at the idea that ordinary, innocent people would never confess to a crime they didn’t commit. In fact, she found that people can be made to do it quite reliably.

In just three one-hour sessions, Shaw was able to convince 21 of her 30 college-age subjects that they’d committed a crime when they were around 12 years old — assaulted another child with a weapon, for instance — and had a run-in with the police as a result. She supplied details that were recognizable to the subjects — the location where the assault supposedly happened, who the other child was — drawn from information their parents provided in a questionnaire. Shaw tells me she designed her study to mimic the techniques used in some false-confession cases. “I’m essentially marrying poor interrogation tactics with poor therapeutic tactics,” she says. The results were so strong, in fact, that she stopped administering the experiment before she had run through her full sample.

John E. Reid & Associates, a training organization that holds the official copyright on the Reid technique, maintains that problems only arise when cops deviate from the Reid formula. “False confessions are caused by investigators stepping out of bounds,” says Joseph Buckley, the organization’s president.

While false confessions that send people to prison are the most serious problem with modern police interrogations, they aren’t necessarily the most common one. Day to day, these practices may undermine good police work in another way: As a confrontational strategy built for extracting confessions, standard interrogation technique can be an ineffective tool for gathering lots of useful and accurate information. Some suspects end up confessing falsely under the glare, but far more do what Campos-Martinez did: They clam up. They sense all too readily that they’re in the presence of “a hunter stalking his game,” and they behave accordingly. A number of scholars have called for a wholesale shift from a “confrontational” model of interrogation to an “investigative” one — one that would redesign interrogations around the best evidence-based approaches to eliciting facts from witnesses and suspects.

Of course, that’s easy to say. If police have stuck by their methods, it’s partly because, in America at least, they’ve had nothing truly viable to replace them with. “Up until now, a lot of the work on false confessions has been about social justice,” says Christian Meissner, a psychologist at Iowa State University. “What we really lacked in the field was an alternative.” Then came the HIG.

A second reformation of American interrogations is quietly under way right now. And it stole into the country via an unexpected route: the war on terror.

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In 2010, to make good on a campaign promise that he would end the use of torture in US terror investigations, President Obama announced the formation of the High-Value Detainee Interrogation Group, a joint effort of the FBI, the CIA, and the Pentagon. In place of the waterboarding and coercion that took place at facilities like Abu Ghraib during the Bush years, the HIG was created to conduct noncoercive interrogations. Much of that work is top secret. HIG-trained interrogators, for instance, are said to have questioned would-be Times Square bomber Faisal Shahzad and convicted Boston Marathon bomber Dzhokhar Tsarnaev. The public knows nothing about how those interrogations, or the dozen or so others the HIG is said to have conducted, unfolded. Even the specific training methods the HIG employs — and that it has introduced to investigators in the Air Force, Navy, and elsewhere — have never been divulged.

At the same time, however, the HIG has become one of the most powerful funders of public research on interrogations in America. Scholars have used HIG funding, for instance, to make a careful study of law enforcement models from England and Canada, which both abandoned Inbau-Reid-style interrogation tactics long ago as unethical and unreliable. In recent years, Canadian police have been moving toward a technique called the “cognitive interview,” a nonconfrontational method that’s meant to get the subject narrating as much as possible — no theming or yes-or-no questions. And for more than a decade, the UK has used a similar method known as PEACE, an acronym that stands for Planning and preparation, Engage and explain, obtain an Account, Closure, and Evaluation. Police in England aren’t even permitted to lie to suspects. A HIG-funded metastudy published in 2014 indicates that PEACE is more effective at producing true confessions and protecting against false ones than an accusatory approach.

In all, the HIG has funded some 60 studies in psychology and the behavioral sciences at universities around the world, digging into what works and what doesn’t in interrogations. Some have focused on how to “prime” witnesses — that is, how to create environments that put people in an open, talkative frame of mind. They’ve learned that people tend to divulge more information when sitting in a spacious room with windows (the very opposite of what the old Inbau-Reid model recommends) and that holding a warm beverage can actually create positive impressions of the people around you.

Other researchers have dabbled in lie detection, but in a way that bears little resemblance to Reid’s emphasis on polygraph results and telltale fidgeting. HIG research is highly influenced by the work of UK-based researcher Aldert Vrij, who studies the “cognitive load” that lying puts on the brain. “Truth tellers ultimately will be able to give you far more detail that you can go and check,” says Steven Kleinman, a veteran military interrogator who has worked with the HIG. “No matter how good the cover story is, it’s not going to be as rich as a real-life story.” Liars, in other words, have to work much harder to invent and keep track of details. One way researchers have found to bring this strain and effort to the surface is to ask witnesses to tell their stories in reverse chronological order: Liars have a much harder time with it.

But the central finding running through much of HIG’s research is this: If you want accurate information, be as non-accusatorial as possible — the HIG term is “rapport-building.” This may sound like coddling, but it’s a means to an end. The more suspects say, the more that can be checked against the record. The whole posture of the interrogation — or interview, as the HIG prefers to call it — is geared not toward the extraction of a confession but toward the pursuit of information.

About three years into its existence, the HIG quietly entered a new phase that marked a significant expansion of the group’s scope and ambition: It set out to start applying its findings in America’s domestic police departments. “We haven’t operationalized enough of the research,” current HIG chair Mark Fallon says. In part, the group just wanted more real-world data, and police departments offered a major source of it. But the bigger goal, Fallon says, was to revolutionize police work with behavioral science, the same way law enforcement procedures were altered a generation ago by DNA evidence and, before that, when the third degree was put to rest.

Los Angeles became the HIG’s first test bed. In 2012, George Piro — a former director of the HIG who had also served as the lead interrogator of Saddam Hussein — approached William Hayes, a captain with the LAPD’s Robbery-Homicide Division, at a conference. Slender, olive-skinned, and fluent in Arabic, Piro was a consummate Fed, a star in Washington for his time with the Iraqi dictator who had drawn the US into two wars. But he was also a child of the Lebanese immigrant community in Turlock, California; before joining the FBI, he had been a detective for 10 years working cases in the Central Valley. He and Hayes connected easily. The HIG, he told Hayes, was looking to fund research into real-life interrogations and needed live data to study. He also wondered whether detectives in the LAPD might be interested in learning more about some of the methods the HIG was developing.

After that first meeting, Hayes arranged for the LAPD to supply the HIG with hundreds of hours of audio from its cases. The response to Piro’s other idea took a little longer. On the face of it, LA is an unlikely candidate for police-suspect rapport-building. This is the town where cops beat Rodney King in 1991, where they killed an unarmed veteran on live TV after a high-speed chase in 2013. What’s more, LA has its own history with false confessions. In 2007, 19-year-old Edward Arch was arrested for murder. He denied being involved dozens of times, but the police recited their theory of the case over and over and suggested they’d be lenient if only he confessed, which finally led him to capitulate. Arch spent three years in jail awaiting trial before a judge ruled that the confession had been coerced and tossed out the case. “I don’t believe it was the officers’ intent to extract a false confession,” Arch’s lawyer told reporters, “but the tactics they used greatly increased the risk of that occurring.”

After a few conversations with Piro, Hayes decided to send Stearns and Marcia to be the LAPD’s guinea pigs. In December of 2013, the two detectives boarded a flight to Washington, DC, to become the first two municipal police officers in the country to undergo HIG training — whatever that was. Neither man was particularly excited. “I’m not a guy that likes to go to training,” Marcia says. “I like to work.” Still, he tried to have a good attitude: “I just told myself, whatever it is, commit to it. Commit to it.”

Like any two detectives on the force, Stearns and Marcia had done a lot of learning on the job over the years — acquiring their own personal, idiosyncratic impressions of what works and what backfires in the interrogation room. Marcia remembers a couple of cases in particular that shook up his thinking. In one, he walked into the room with the suspect and, à la Reid, said, “Look, there’s no doubt in my mind that you committed this crime. We have this. We have this. We have this.” To which the suspect said, “Well, if you think you know all that shit, I got nothing to say to you.” Then he recalls another case, a murder, in which the suspect ended up confessing to the crime after two and a half hours of quiet conversation. “I never raised my voice. I never cussed.”

Stearns, for his part, often thinks back to one case in particular — the 2009 arrest of one of the department’s own detectives, Stephanie Lazarus, for a murder she committed in the 1980s. The Lazarus case was unlike any he had worked before, and it landed him in the national spotlight for a brief moment. Lazarus had covered her tracks immaculately after going to an ex-boyfriend’s house and killing his new wife; the original investigators never treated her as a suspect. In preparing to interview her 20 years later, Stearns says, he and his colleagues knew this could in no way resemble a traditional interrogation. They created a ruse, inviting her to come in and advise them on a case involving stolen art. Knowing they were dealing with one of their own, they rehearsed and prepared for the interview more than Stearns remembers ever doing before. When the conversation turned to the murder, they stayed chatty and nonconfrontational for as long as possible. In a crucial moment, they got her to acknowledge she’d known the victim and had even confronted her at the hospital where she worked. This was interrogation as a poker game. “It was almost, I guess, 'Colombo'-esque,” Stearns says, “making her feel like she really had the upper hand, when in fact we’d been working nonstop for days and had a really strong grasp of the evidence.” On March 8, 2012, Lazarus was convicted of first-degree murder.

At the HIG, Marcia and Stearns discovered that many of the things they’d picked up from experience — these practices that were out of line with the old image of the tough-talking interrogator — were validated by research. They learned, for instance, that the kind of advance preparation and strategy that Stearns had put into the Lazarus case, and his unusual efforts to keep the conversation noncombative, have been shown to be effective. They marveled at how this model of interrogation was practically a team effort. All interviews are monitored in real time by colleagues, and the interviewers take breaks, going outside to get advice — “almost like you’re going to the corner in between rounds,” Stearns says, “and you’ve got your trainer who’s telling you, hey, you got to start bringing up your left.”

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By the time Stearns and Marcia returned from their week of training in Washington, the HIG was starting to become a known entity among detectives at headquarters. Piro had visited, lecturing to more than 100 officers about his time in the box with Saddam. Detectives in the department were eager to test out the new approach. And they were still vexed by the Medellin case. So the original investigators of the murder asked Stearns and Marcia if they wanted to take a crack at Campos-Martinez using what they’d learned. If not an outright confession, maybe they could score some admissions or denials that might be squared with other evidence in the case. “They wanted someone else to take a shot,” Stearns says, “so we agreed to do it.” It was the first time these new methods would be used in a regular American criminal case.

In the early afternoon of March 9, 2014, Campos-Martinez met Stearns and Marcia at the hotel where the detectives were staying in San Antonio, an old-fashioned establishment across the street from the Alamo. The cops were both tall and broad-shouldered; Marcia had a bushy mustache, Stearns a pompadour and sideburns. Suitcases and maps and papers were strewn about the hotel suite. But there were no tape recorders in sight, no pads with questions. Campos-Martinez, who was dressed in his convention-center work clothes, said he only had about half an hour. That’s fine, the detectives said. Whatever time he could spare.

Stearns and Marcia said they wanted to hear his side of things. They sat down together, just three guys talking. When Campos-Martinez spoke, they almost never interrupted or even asked that many questions. It was the strangest thing. He should have been on his guard. But the less the police talked, the more he did.

As they listened, Stearns and Marcia painstakingly avoided “theming” in front of their suspect, even though they had, in private, agreed on a set of working hypotheses about his potential motives. They noticed, for instance, how quickly Campos-Martinez had established a completely new life as a conventionally married man in San Antonio. This indicated to them that he was, if nothing else, fiercely adaptable — a survivor. They knew he and Medellin had been arguing. They wondered if Medellin had been talking about ending things. Campos-Martinez was undocumented, and the detectives figured he was painfully aware of how precarious his life was. (The LAPD had never used his immigration status against him for fear of sending Campos-Martinez out of the country, where they would lose him forever.) “He had wound up living in this comfortable little apartment, having this comfortable little life, having a guy who had a pension and financial stability and security.” And maybe he feared he was going to lose that. So he took action. “Basically what he tried to do is he tried to assume Hervey’s life,” Stearns says. “He was going to do what he had to do to make things work for him.”

They had designed the entire interrogation to prevent Campos-Martinez from feeling cornered or trapped in any way. “Without saying it explicitly, we implied that he was a victim in the case, because he was the one who had suffered a loss,” Stearns says. “He can’t really call that bluff. He has no way of saying, well, that’s not what you guys believe.”

When he grew more comfortable, Campos-Martinez started to reminisce, telling stories of how he and Medellin used to go on walks together in those hills near the Hollywood sign — the same area where the remains were found. Stearns and Marcia encouraged him to relive those walks, and he obliged. He talked about how the sun felt on his face, how it smelled outside.

Now and then Stearns or Marcia would excuse themselves from the conversation, saying they needed to call the wife or check in with the office. But really they were running down the hall, where a consultant to the HIG was watching everything on video alongside the lead LAPD investigator in the Medellin case. “They were tracking everything he was saying,” Stearns remembers. “Tracking checkable facts. They’re telling us to leave a certain area and move on, or to determine trigger points where he might become less cooperative.”

When talk turned to the hours around when Medellin was killed, the detail drained out of the suspect's recollections.

Ultimately, Campos-Martinez stayed in that hotel room for five hours. He called in sick for work, and then he called his wife to say he’d be home later than expected. It was almost like he appreciated the chance to talk. As the hours went on, the conversation started to go in unpredictable directions. He talked about being angry at Medellin — and how, with his lover out of his life, he was thinking he might have a chance at a fresh start. As soon as the conversation moved to the hours around when Medellin was killed, the detail and color drained out of his recollections. “The narration became more and more fragmented,” Stearns says. In light of the detectives’ HIG training, that blurriness spoke volumes. Campos-Martinez also told the detectives that Medellin had called him from Mexico — on days when the police knew he’d received no such calls.

Another decisive moment came four hours into the meeting, when Campos-Martinez talked about a plant called Datura, which can be made into a medicinal tea but can also be toxic. “He intimated that it could cause someone to be incapacitated,” Stearns says. The district attorney who would go on to prosecute Campos-Martinez, Bobby Grace, took special notice of this detail. After all, the killer would have needed to immobilize Medellin somehow before hacking him up.

When the detectives said good-bye, Campos-Martinez looked relaxed. Considering how long he had voluntarily lingered with the cops, he may have thought he had nothing left to worry about. After all, it hadn’t felt like an interrogation. But later that same day, the Los Angeles district attorney’s office issued a warrant for his arrest.

By now, the HIG has trained 35 detectives in Los Angeles and is coming back to train more. “The LAPD is sold on it,” says Mark Severino, a 29-year veteran of the force who is currently a detective supervisor with the Major Crimes Division.

Since that first interrogation by Stearns and Marcia, Severino’s unit has conducted about 60 interrogations using HIG methods, he says — in cases involving human trafficking, murder, and terrorism. Severino has modified his interview room to be more welcoming and tries to have his detectives talk to witnesses and suspects as soon as they’re identified, to set the right tone for the interviews. “We make our living talking to people,” Severino says. “And the HIG teaches us the best approaches—how to gain people’s trust.” By not single-mindedly seeking out confessions, Severino has found that he’s netted enough information from some suspects to amount to an admission of guilt. In other cases, he’s learned enough to eliminate persons of interests as suspects altogether. In still other instances, he says, they “were able to identify crimes in the planning stage and stop them before they occurred.” Severino has asked other divisions of the LAPD to grade his division’s success rate, based not just on whether they secured a confession but on whether they uncovered new information that helped the case. “Right now we’re at about a 75 to 80 percent success rate,” Severino says. “When you’re interviewing a witness, this system does work.”

Of course, just because some LA detectives have been influenced by a new evidence-based interrogation method doesn’t mean all cops will. Even in LA, Stearns and Marcia are meeting with some resistance as they move to develop department-wide training in the tactics. Police veterans aren’t exactly eager to be told they’ve been doing their job wrong for 30 years. “I think we can overcome that pushback by focusing on the younger guys in our division,” Marcia says. There’s an entrenched culture behind that blue wall — and a new, labor-intensive technique based on “rapport-building” might not be the most likely thing to breach it. “Interrogation and interview is a very egocentric thing,” Stearns says. For some police departments, and for some interrogators, it may be a nonstarter to do anything other than treat a suspect with suspicion.

Still, the researchers and academics who’ve worked with the HIG are determined not to lose momentum. They think they have a real shot at changing the culture of policing. “Law enforcement is hungry for something new and evidence-based,” Meissner says. “They know there’s an issue with false confessions, and they’re looking for an alternative.” The HIG’s Mark Fallon, meanwhile, is doing the rounds at the nation’s police departments.

Campos-Martinez never did confess. But thanks to his remarks about poisonous tea and the fuzziness of his account of the hours around when Medellin died, the LAPD’s investigation finally gathered enough information to make a case against him. On November 16, 2015, he was sentenced to 25 years to life in prison for the murder of Hervey Medellin. The sentencing judge called the crime “so inexplicable, so depraved ... it defies description.” The verdict and sentencing furnished the media with more occasions to bring up the head found beneath the Hollywood sign and all the other lurid trappings of the murder. From start to finish, people covering the case had been scarcely able to resist pointing out, in some way or another, how like a movie it all was. But what no one outside the LAPD really realized was just how much the case turned Hollywood detective story tropes on their heads. The interrogation room was a pleasant midrange hotel suite. And the hard-boiled detectives, despite looking like cops straight out of central casting, were working from an entirely new script.

An earlier version of this story incorrectly stated that Christian Meissner works at University of Iowa. He works at Iowa State University.