Different people tell the same story in different ways. An academic will tell it one way, a journalist another, and a filmmaker a third. All try to get at the truth in their own fashions. In telling the story of Carlos DeLuna, a young Corpus Christi man executed in 1989 for murder, that means ultimately trying to figure out:

Did DeLuna really stab Wanda Lopez to death in 1983?

Another way of putting it: Did Texas really execute an innocent man?

DeLuna’s story has been told numerous times, by the Corpus Christi Caller-Times back in 1983, by the Chicago Tribune in 2006, by a team from the Columbia University Law School in 2012 and again in 2014. The latest telling is The Phantom, a brooding documentary by British filmmaker Patrick Forbes that premiered at the Tribeca Film Festival in June and opens in theaters July 2. The film takes viewers to places that readers of a newspaper story or a law-school journal might only imagine. For example, The Phantom opens with the literal sounds of murder. It’s the actual tape of Lopez, 24, a clerk at a Sigmor Shamrock station, calling the Corpus police on the night of February 4, 1983, and, as you watch a reenactment onscreen, you hear her go from quiet fear—“I have suspect with a knife,” she says calmly—to frantic terror a few seconds later as she begs, “You want it? I’ll give it to you!” Finally, you hear her screams as the killer stabs her in the chest.

Forbes first learned of the infamous DeLuna case in 2012, when he was in Austin because his documentary Wikileaks: Secrets and Lies was showing at South by Southwest. “I thought, ‘This is an incredible story—a guy who says he’s innocent and is executed anyway. It’s all about the truth—and your notion of the truth.’ I thought, ‘I’m in.’”

Forbes was lucky to ever hear DeLuna’s story in the first place. Back in 1983, the murder of Lopez seemed to be an open-and-shut case. An eyewitness at the Sigmor named Kevan Baker locked eyes with the killer and gave the police a description: a Hispanic man wearing a gray sweatshirt or flannel shirt. Police fanned out, using Baker’s words, but also those from a couple who had seen a Hispanic man in a white shirt running nearby. About 45 minutes later they found Carlos DeLuna, age twenty, hiding under a truck. DeLuna was a troubled young man—a seventh-grade dropout who had an IQ of 72. He had more than twenty crimes on his record, mostly minor offenses like public drunkenness, though he had once pled no-contest to attempted aggravated rape and driving a stolen vehicle and spent a couple of years in prison. The police put him in a cruiser, brought him back to the crime scene, shone a light in his face, and asked Baker if this was the guy. Baker wasn’t positive—he was nervous and remembered a mustache on the killer—but he said yes.

The crime scene was a bloody mess, and though DeLuna had no blood on him, he was arrested. Police found a lock-blade knife, but they weren’t able to lift any prints from it. DeLuna was given a couple of public defenders and offered a deal—plead guilty and get a life sentence. He refused, saying he wouldn’t confess to something he didn’t do. DeLuna said he knew who had killed Lopez, but he wouldn’t tell anyone because he was scared the man would somehow exact revenge. By the time DeLuna finally told his lawyers the man’s name—Carlos Hernandez—it was too close to trial to do much of an investigation. When DeLuna claimed on the stand that he had been with Hernandez that night at the gas station but his friend was the actual killer, one of the prosecutors mocked him by calling Hernandez a “phantom.” DeLuna was found guilty, sent to death row and, six years later, executed by lethal injection. He proclaimed his innocence to the very end.

In 2003, Columbia Law School professor James Liebman came upon DeLuna’s name while studying Texas death sentences founded on eyewitness testimony. Wanting to know more about the case, he sent an investigator to Corpus, who quickly found a couple of interesting—and disturbing—things. First, Carlos Hernandez (who had died in prison in 1999) was no phantom; he had a long criminal record. Second, back in 1983, DeLuna and Hernandez had remarkably similar faces and bodies. Liebman and his students investigated further and found that Hernandez had a reputation for being a mean-spirited, violent man with an affinity for cutting women with a lock-blade knife. He had once been arrested for killing a young mother and carving an X on her back (the case was later thrown out). The team even found a woman who said Hernandez had confessed the Lopez murder to her.

To Liebman, it was clear that Hernandez was the killer but police had been so focused on DeLuna that they had never properly investigated. For example, once the cops arrested DeLuna, they had shut down the crime scene; they didn’t even collect any blood from the floor and they never analyzed a bloody shoe print. Liebman wanted someone to corroborate his findings, and so sent them to two Chicago Tribune investigative reporters, Maurice Possley and Steve Mills. They traveled to Corpus and found five different witnesses who said Hernandez had bragged about killing Lopez. The journalists learned that many people in the law-enforcement community knew all about the violent Hernandez; a detective who was not assigned to the Lopez murder told them that informants had told him Hernandez was the killer—info he said he passed on to the case detective. Possley and Mills also talked to Baker, the eyewitness, who said he was only 70 percent sure DeLuna was the killer. “I wasn’t all that sure,” Baker told them, “but him being Hispanic and all . . . I said, ‘Yeah, I think it is him.’ The cops told me they found him hiding under a truck. That led me to believe this is probably the guy.”

The Tribune published a front-page, three-part series in 2006 that made Possley and Mills finalists for a Pulitzer Prize. A few years after that, Liebman and his students began compiling all the evidence into a four-hundred-page report that took up an entire issue of the Columbia Human Rights Law Review. In 2014, those results were edited further and turned into a massive book called The Wrong Carlos. It was clear, Liebman wrote: DeLuna did not kill Lopez. The book was widely praised, and many thought the journalists and researchers had proven that Texas had executed an innocent man. Supreme Court justice John Paul Stevens certainly thought so. In 2015, he stated that Liebman had shown “beyond a shadow of a doubt that there is a Texas case in which they executed the wrong defendant, and that the person they executed did not in fact commit the crime for which he was punished.”

It’s one thing to say that, though, and another thing entirely to prove it—and legally exonerate a dead man. To do that, you would need something like DNA evidence pointing to someone else. The best place to find such evidence would have been the items collected from the crime scene, such as the knife and a pack of cigarettes left on the counter by the killer. Unfortunately, in 2004, when Liebman and his team went to the courthouse looking for the evidence, they were told it was nowhere to be found. Liebman later found a motion from the DA’s office (filed soon after the trial was over) “requesting the court’s permission to withdraw all of the exhibits.” When Forbes came along 13 years after that, he was also told the files were missing—and even went to two different storage facilities to look for the boxes (he visited one five times). “The records are in complete chaos,” he said, “and everything was covered in dust.” He’s convinced the evidence is lost to time.

Forbes isn’t a lawyer, he’s a filmmaker, so while The Phantom provides no new tangible proof of DeLuna’s innocence, it lays out every other kind of evidence, in a vivid, creative, neo-noir style. The Phantom takes viewers back and forth between the 1980s and today, from the mean streets of the Corpus barrio to the clean hallways of the modern-day justice system. Forbes uses stylized reenactments; a focus on inanimate objects (clocks, an old-fashioned tape recorder); and pulsing, synthesized modern music (by British film composer Rob Manning) to push the story along in gripping fashion. The Phantom has the same eye-opening feel of another great Texas-related documentary, The Thin Blue Line, Errol Morris’s influential 1988 film about the wrongful conviction of Randall Dale Adams in Dallas.

Forbes set out to interview everybody involved in the case, including many with whom previous researchers never spoke. They all wanted to talk. “They all have the attitude that we should resolve this,” he said, “and clear the stain from this town.” He filmed these people in locations where the actual events took place—outside the service station; inside the courtroom. Some of his most important interviews were with people who were on the scene the night of February 4, 1983. Policeman Bruno Mejia told Forbes that in the chaotic minutes after the murder, he realized they were probably chasing two Hispanic men, one in a flannel shirt and one in a white shirt. Then, while the crew was filming a reenactment at the Sigmor, they were approached by a neighborhood man who remembered that night. He was watching Jaws, he said, heard a commotion outside, and went to his window, where he saw one man run by and hide under a truck. “Then about thirty seconds later,” Raymond Nunez says in The Phantom, “I see another person running down the street.” Forbes was thrilled. “It proves that what DeLuna said was true: there were two people running away from the gas station.”

Good filmmakers, like good lawyers, know they have to use both logic and emotion to make their cases. Forbes filmed his interview subjects up close, their agonies conspicuous on their faces after all these years: the brother still haunted by his refusal to help his troubled sibling, the rookie TV journalist who went from certainty at DeLuna’s guilt to weeping after a final conversation with him an hour before his death, the death-house chaplain who still can’t get DeLuna’s execution out of his head. “Here is one of the biggest mistakes Texas has ever made,” says Carroll Pickett, the chaplain at death row from 1982 to 1997, who held DeLuna’s leg while he died. “He’d done some things before that, he admitted that, but he didn’t do this one and they killed him anyway.”

Some of Forbes’s best interviews are with Hernandez’s many victims. It’s one thing to read newspaper accounts of people saying he bragged about the murder and terrorized them—and another to see their wan faces and hear their tired voices. One tells how Hernandez would regularly beat and rape her. “It would be him, me, the baby, and the pillows, then the knife under the pillow. He would be talking to it, just like if it was a person.” Another shows the scar on her stomach where Hernandez stabbed her. As these women tell it, Hernandez left scars all over Corpus.

Forbes is a big fan of The Thin Blue Line and knows it is considered one of the great documentaries of all time, not just for its style but also its effect: the film helped exonerate Randall Dale Adams after the actual killer confessed onscreen. Forbes doesn’t have that kind of luck here—he can’t rescue a dead man. But he’s crafted an important film for the living, one that shows how easy it is to be in the wrong place at the wrong time—and how simple it was for the state of Texas to make a terrible, irrevocable mistake. The Phantom is ultimately a warning about capital punishment. “The fundamental problem with the death penalty,” said Forbes, “is it depends on certainty, in a world where there can’t be certainty. You don’t know what the truth is.”