In the late 1990s, Osama bin Laden was bumped out of the FBI’s “10 Most Wanted Fugitives” list by a man named Angel Resendiz.

He was a Mexican-born drifter who criss-crossed the United States by freight train for more than a decade, hopping off at random and bludgeoning his unsuspecting victims to death. The modus operandi led to his moniker, “The Railroad Killer.”

Resendiz was finally arrested by Texas Rangers in July 1999, after giving himself up on the international bridge at El Paso. I met him four years later in prison, where he claimed he was half-man, half-angel and that he was ridding the world of sinners. But his victims weren’t sinners—they were a schoolteacher, a student, a pastor and his wife, an elderly man and his daughter. They lived in towns and cities all across America—Texas, Florida, Kentucky, Illinois. Nowhere was safe.

At his trial, he was convicted of just one murder: that of Houston doctor Claudia Benton, whom he raped and stabbed repeatedly before smashing a statue into her skull. His attorneys claimed he was insane and didn’t understand the ultimate penalty he faced, but they admitted he had murdered nine people during his killing spree. After jurors returned a guilty verdict, Resendiz spoke of his desire to die.

“I’ve decided that injection is better than spending life in jail," he said.

In 2006, at the time of his execution, the number of victims authorities reckoned he had killed had swollen to 15.

When I interviewed him he had waived most of his appeals in an attempt to speed up his journey to the execution chamber. In my notebook I remarked that he didn’t seem physically capable of the horrendous crimes he’d committed. He was small, overweight, and wore glasses. But I was taken aback by the almost matter-of-fact way he told me: “Sometimes I used to chop some bodies and throw them in the swamps.”

I remember his eyes—black, staring—and the childlike enthusiasm with which he devoured the donut and Coke I had just bought him from the prison’s vending machine (delivered to him by a corrections officer).

It was cold in the large visitation room that morning back in 2003, near the wing of the east Texas prison that houses the state’s death row inmates. Resendiz was somewhere in the middle of a bank of tiny box-like cells, separated from me by bulletproof glass. After the door behind him was locked, he had pushed his cuffed hands through a metal slot and a corrections officer un-cuffed him.

We spoke via phone, albeit inches apart, and in that hour the murderer began confessing to other crimes—other slayings, he told me, casually, that the police weren’t interested in, or which hadn’t been properly investigated. He seemed keen to elucidate on the additional murders—as much as he could, considering the passage of time.

At one point he attempted to show me where he had tried to mutilate his genitals in prison—until I asked him to stop.

“Do you fear death,” I asked?

“I fear God,” he replied. “That’s about it. I fear no one else but God.”

One of the confessions he made during that interview was to the killing of “three or four” people “on the border of Arizona and California” that he said authorities didn’t know about.

Another took place five years earlier, he said, but two other people had been convicted of that crime.

“They got life in prison,” he told me, almost excitedly, “because of what I did.”

In June 1998, 36-year-old Darryl Kolojaco was bludgeoned to death with a steel pipe in the living room of his Houston home. Within days police had focused in on his estranged wife, Diamantina Kolojaco, and her lover Andres Mascorro.

The state’s case against Diamantina Kolojaco and Mascorro was, on the face of it, pretty convincing. At the time of his death, Darryl Kolojaco carried $100,000 worth of life insurance, and Diamantina Kolojaco was the primary beneficiary.

When detectives arrived at the murder scene, Diamantina Kolojaco told them she believed her husband was bisexual and that this fact could have had something to do with his murder. Two days later she made a written statement admitting she planned to remove her sons from the house the night of the murder so that Darryl Kolojaco would be alone—and that she wanted him killed so she’d receive the proceeds from the life insurance policy.

Her statement implicated Mascorro, an undocumented construction worker with whom she was having an affair. After detectives arrested Mascorro and showed him Diamantina Kolojaco’s confession, he too signed a written confession stating he killed Darryl Kolojaco by beating him with a steel pipe.

The case, prosecuted by Harris County, seemed cut and dried. Diamantina Kolojaco and Mascorro were tried, convicted, and sentenced to life in prison in 1999.

Then, two years later Resendiz wrote to his trial judge claiming he had killed Darryl Kolojaco; that the man had picked him up at a day labor spot and taken him back to his house where Darryl Kolojaco had made a pass at him. That's why he had killed him, Resendiz said.

But nothing had happened as a result: Resendiz was executed a few years later and Diamantina Kolojaco and Mascorro remained in prison.

“ I never really knew how much one signature would be worth in the state of Texas. I had no idea. ” — Andres Mascorro

I moved back to the UK shortly afterward and I wrote about Resendiz for a small magazine in London. I thought I’d lost the old C-90 cassette tape of our interview. In 2015, when my wife and I moved back to Texas, I found it at the bottom of one of the countless cardboard boxes in which we'd packed our lives.

I listened back to those confessions—knowing that two people were still in prison, all these years later, for a murder Resendiz had told me he’d committed.

A couple of years on, following a lengthy conversation one evening with an old friend, Pete Sale, an audio producer in London, we decided to make a podcast series together, following up on this and other confessions Resendiz made to me all those years ago.

We called it “Dead Man Talking” and had a wish list of interviewees, at the top of which were Diamantina Kolojaco and Mascorro.

I’d written to Mascorro in the past but never received a reply. It struck me that he may still not speak English and so I sent him another letter—this time in Spanish—and within a couple of weeks, he wrote back. The reply just said: come and visit me.

Mascorro is housed at Texas’s McConnell Unit, south of San Antonio, and we spoke through an interpreter. He said the day he was arrested he was told Diamantina Kolojaco had confessed to wanting to kill Darryl Kolojaco for the money, implicating him.

“I got very scared for my family because they told me [they] would be beaten and deported,” he said.

He explained that he and his brothers were living in the U.S. illegally. He also said he never once had an attorney present during his interrogation. “They didn’t let me make one phone call—nothing. They told me: sign here and you’ll get out.”

Mascorro said the confession he was asked to sign was written in Spanish but that it had clearly been translated from the English by someone who was not fluent.

“I never really knew how much one signature would be worth in the state of Texas. I had no idea,” he said.

He told me that at the time of Darryl Kolojaco’s murder he was with Diamantina Kolojaco’s children. “During my trial, the youngest one even went up and testified for me.”

But the jury didn’t believe him.

Over the years I’d exchanged a handful of letters with Diamantina Kolojaco. Since her conviction, she’d been housed at a women’s prison in Gatesville, Texas, not far from Waco. Despite her infidelity, she told me her relationship with Mascorro was an open one and that at the time she still shared a home with Darryl Kolojaco.

The night he was murdered, she had been shopping with her two sons, Alex and Jose, and she said after they pulled up in the driveway, while she and Alex began pulling bags out of the pickup, Jose opened the front door of the house. “He came running back out and grabbed me and said don’t go in there…. Darryl’s dead.”

I asked her why she had signed what amounted to a confession. She said she didn’t have her glasses on and wasn’t aware what she was signing; that the detective had told her it was a record of everything they had been talking about.

Diamantina Kolojaco told me she had no family left to turn to or money to pay a lawyer to investigate.

“ His physical descriptions of the scene were something that only someone who had been there would know. ” — Les Ribnik, Resendiz’s lawyer

But there was something else. She’d told me that Resendiz had written to her, too, confessing to the murder. In the letter, which she said was subsequently confiscated by corrections officers, he had apologized that she was in prison because of him.

“He described some of my house,” she said, “But how would he know? He said up the stairs there was a big old canvas painting, which there was; that the carpet was pink and yes it was.”

And nothing happened as a result? I asked.

“Nothing,” she said.

It turned out I wasn’t the only reporter he’d confessed to either. Resendiz had told Mark Babineck from the Associated Press the same thing―that he had killed Darryl Kolojaco, and that Diamantina Kolojaco and Mascorro had been wrongly convicted of the murder.

I tracked down Babineck, who now works in the energy industry, at his home in Houston and he told me that after Resendiz had volunteered information about the Kolojaco murder, he’d driven to the house. There were all these descriptions Resendiz had given him—“oddly specific in some cases,” Babineck said, “like the shape of the fence. Things like the water tower… and sure enough it all checked out.”

The Kolojaco crime scene was exactly as Resendiz had described. I asked Babineck if Resendiz could have found out the information from reading newspaper reports, but he said that would have been next to impossible. He had described things like the particular serpentine shape of a wooden privacy fence—“why on earth would that have been mentioned in an newspaper?” Babineck said, particularly about a case that wasn’t even covered that closely.

Babineck told prosecutors what he’d learned: that a known serial killer was divulging specific details about the Kolojaco murder. “But they were confident in their case and said he might have picked up those details somewhere in the prison system. But as far as I could find he had never served time in any institution in the ensuing years with anyone involved in that case.”

After that, Babineck said he was forced to drop the issue. “You move on,” he told me. “You’re one of four wire service reporters covering the nation’s fourth largest city. But the level of those oddball details has always kind of stuck with me.”

A few weeks later, Les Ribnik, one of Resendiz’s appellate lawyers, showed me photographs he'd acquired from the Kolojaco crime scene.

“Resendiz mentioned a picture on the wall of the Santa Maria, Niña and Pinta,” Ribnik said. “His physical descriptions of the scene were something that only someone who had been there would know. He also described the swimming pool; said its corners were scalloped. And it didn’t make any sense until I saw it for myself.”

It seemed incredible that two people could end up dying in prison for a murder that one of America’s most notorious serial killers credibly confessed to committing.

I’d been trying to get a lawyer to look at the cases of Mascorro and Diamantina Kolojaco. But I wasn’t prepared for what would happen next.

I asked an appeals court in Texas to send me the full trial transcripts for both defendants. After several weeks they sent me a copy of Mascorro’s, but remarkably it turned out they had lost Diamantina Kolojaco’s; apparently the court's archives were being moved from one building to another and hers had been mislaid.

Over the Christmas holiday, I got a call back from the South Texas College of Law in Houston. Cathy Burnett, the college’s vice president and director of the pro bono honors program, had gone through Mascorro’s court transcripts in detail with her final-year law students. She hadn’t told them about the podcast, nor about Resendiz’s confession, so that they’d read the record cold. If we disregard his confession, she wondered, how strong was the evidence against Mascorro?

Burnett’s students thought the case was 100 percent circumstantial, and when I visited her a few weeks later at her office in Houston, she said they found a number of things concerning. They thought the Spanish translation of the confession he signed was bad; that Mascorro was in custody for a long time before he confessed; that his original statement was torn up and thrown away; and his statement wasn’t videotaped.

There was no DNA evidence linking Mascorro to the crime scene at all. Blood on a towel found in Mascorro’s car was his own and not the victim’s—and yet the jury was told about it. “He’s a carpenter,” Burnett told me. “He testified he’d had an accident at work or hit his thumb with a hammer and then the blood blister broke. What’s unusual about that?”

She also described some “uncomfortable racial overtones” to his prosecution; that during the state’s concluding arguments “the jury was invited several times to think about the defendant’s culture and where he came from.”

Burnett said that it sounded to her as if in summing up, the prosecution was inviting the jury to think that the defendant was macho; that Darryl had thrown something at Mascorro and that he’d flown into a jealous rage.”

“Think about where the defendant comes from, Think about his culture,” the prosecution said in summing up toward the end of the trial. “Think of the Mexican culture… Based on his culture, jealousy, I believe is the reason for what he did.”

The biggest bombshell in Burnett and her students’ assessment of Mascorro’s case, though, was this: the court record showed that near the beginning of the trial his defense counsel had asked for what’s known as a motion of continuance—essentially a pause in proceedings. There were still witnesses they wanted to locate and speak to, they said.

“Are these newly discovered witnesses?” the judge asked.

“One of them is,” said Judith Prince, one of Mascorro’s representatives.

This witness was actually a United States marshall who had apparently visited the crime scene shortly after Darryl Kolojaco’s murder, and who had been showing photographs around the neighborhood “of a possible suspect in the killing who was not our client.”

The entire exchange only warranted a few short lines in the trial transcript, and the judge denied the motion. The trial continued without the marshall ever being interviewed by the defense.

“This is something that really bothered me, for two reasons,” Burnett told me. “It seems to suggest that there was someone else who was a person of interest to law enforcement. That’s huge. Who was that person of interest?

“The second reason is because it was the feds. Normally in a regular murder case, even a horrible, brutal slaying like this, the federal government doesn’t get involved. These are matters for states. The prosecution occurs at the state level, not at the federal level. So if we have the feds involved, why? Do they suspect that perhaps the perpetrator here is someone who is committing a series of crimes across many jurisdictions?”

Could this suspect have been Resendiz?

A representative from the U.S. Marshals Service told me the agent in question still worked there and asked me to send him the relevant section of the trial transcript. “He does not recall the case,” he wrote back. “We remember the Resendiz case as we assisted that one as well.”

I asked whether the possible suspect the agent was inquiring about at the time of the Kolojaco killing could have been Resendiz.

“Maybe,” he wrote.

Burnett said she believed there was enough to file what’s known as a habeas petition—a legal move used to bring a prisoner before the court again to determine if their imprisonment is unlawful.

If the trial judge agreed with the petition, they could then send the case to the Texas Court of Criminal Appeals.

“If we have strong evidence of someone else being the actual murderer and there is absolutely no physical evidence linking Mascorro to the crime; no people who put him at the scene; no eyewitness testimony… then at trial we have a prosecutor who has yet another theory [in addition to murder for remuneration]—of macho Mexican culture; jealousy—when we balance the lack of evidence with someone else’s confession then I think all of us are left with a sense that someone else is the real actor. And in that case I think you’ve got a shot at a writ.”

If a habeas writ were successful, what would happen to Diamantina Kolojaco―whose court documents have disappeared?

“If it’s shown that someone else absolutely not connected to her committed the crime,” Burnett said, “then I think she would be in a good posture to say the state’s theory was never that she was the perpetrator… she was never the one striking the blows; she was the person directing her lover to kill her husband, and if her lover didn’t kill her husband and he was killed by someone else, do we even really care that there is no longer a court record?”

Part of any future habeas petition would likely include the confession that Resendiz made to me. “I think that’s huge,” she said, adding if we could find an attorney to actually file the writ, she and her students would be willing to do the background research and write the brief.

A mutual friend had introduced me to a man named John Hardin who she said might be able to help. Hardin ran a nonprofit called Proclaim Justice, which fights wrongful convictions.

He had been inspired by a high-profile case known as the West Memphis Three in the 1990s in which three teenagers were convicted of the ritualistic murder of three 8-year-old boys. Legal developments involving newly tested DNA evidence that didn’t implicate them led to the three men entering what are known as Alford Pleas in 2011, allowing the state to maintain their convictions but meaning they could be released from prison and publicly maintain their innocence.

One of the three, Jason Baldwin, teamed up with Hardin to launch Proclaim Justice, which investigates possible cases of wrongful conviction and raises money to pay for attorneys.

Hardin and one of his investigators have already begun digging into Mascorro’s case, which he described as troubling. “We’ll take our time and spend resources investigating and re-interviewing witnesses,” he told me.

He said it may take them a few months, but if they decide to take on the case they would secure a post-conviction attorney to represent Mascorro and they would partner with Burnett and her team at South Texas College of Law.

“It’s frankly tough to get a [potential] innocence case looked at… nationwide we’re all overwhelmed with folks maintaining their innocence and wanting an organization to look at their case. For us to get to this point on this case is a good sign.”

Harris County District Attorney’s office told me the Kolojaco case was handled by that office “several administrations ago, and the prosecutors have moved on… In the event any defense lawyers file any appellate type motions, our comment would be from those documents at that time.”

The one thing we’ll never have to help with any potential legal action in the case is the possibility of following up with the person who may very well have committed the crime: Angel Resendiz, the Railroad Killer.

Instead, what we have is his 15-year-old confession and the fact that the fate of two people may well depend on an old C-90 cassette tape.

Dead Man Talking is available on Apple Podcasts, iTunes, Stitcher, or wherever you get your podcasts.