The victim was shot nine times with a rifle during an attempted robbery before the gunman unloaded more rounds into the only witness.
That witness, Juan Moreno, told the Houston Chronicle for its Sunday editions that Cantu wasn't the killer. Moreno said he only identified him at the 1985 trial because he felt pressured and was afraid of authorities.
The doubts now being raised come too late for Cantu. He had long professed his innocence but was executed in Texas on Aug. 24, 1993, at the age of 26.
"You've got a 17-year-old who went to his grave for something he did not do. Texas murdered an innocent person," Cantu's co-defendant, David Garza, said.
Garza, who was 15 at the time of the murder, recently signed a sworn affidavit saying he allowed his friend to be accused even though Cantu wasn't with him the night of the killing.
The Chronicle reviewed hundreds of court and police documents in its investigation of the case.
On the night of the attack, 19-year-old Moreno and his friend, 25-year-old Pedro Gomez were sleeping in a house they were helping build for Moreno's brother. They awoke to a pair of teenagers demanding money, one who was carrying a .22-caliber rifle. Gomez was killed; Moreno was shot but survived.
Moreno was shown a photo of Cantu after rumors at his school that he had been involved, but Moreno didn't identify him as the shooter, the newspaper said. But about four months later, Cantu was involved in a bar shooting that injured an off-duty police officer. Though accusations he shot the officer were dropped, Sgt. Bill Ewell reopened the Gomez case.
A bilingual homicide detective was sent to Moreno's home to show him another photo of Cantu. He didn't identify him.
The next day, Moreno, then an illegal immigrant, was taken to a police station and again shown Cantu's photo. This time, he picked Cantu out from among five photos, according to an officer's report.
"The police were sure it was (Cantu) because he had hurt a police officer," Moreno said in a recent interview. "They told me they were certain it was him, and that's why I testified."
Ewell, now retired, told the Chronicle, "I'm confident the right people were prosecuted."
The district attorney who handled the case, Sam D. Millsap Jr., said though that he never should have sought the death penalty in a case based on testimony from an eyewitness who identified a suspect only after police showed him a photo three times.
Miriam Ward, forewoman of the jury that convicted Cantu, said the panel's decision was the best they could do based on the information presented at trial.
"With a little extra work, a little extra effort, maybe we'd have gotten the right information," Ward said. "The bottom line is, an innocent person was put to death for it. We all have our finger in that."
Since executions resumed in 1982, Texas has executed 355 inmates, according to the Texas Department of Criminal Justice.