Ruben Cantu was 17 in 1984 when he was charged with capital murder in the fatal shooting of a man during an attempted robbery in San Antonio. The victim was shot nine times with a rifle before the gunman unloaded more rounds into the only eyewitness.

The eyewitness, Juan Moreno, told the Chronicle that it wasn't Cantu who shot him. Moreno said he identified Cantu as the killer during his 1985 trial because he felt pressured and was afraid of authorities. (Watch the reporter investigating the case -- 3:16)

Meanwhile, Cantu's co-defendant, David Garza, 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.

Cantu was executed at age 26. He had long professed his innocence.

"Part of me died when he died," said Garza, who was 15 at the time of the murder. "You've got a 17-year-old who went to his grave for something he did not do. Texas murdered an innocent person."

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 during the 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."

Sam D. Millsap Jr., then the Bexar County district attorney who decided to charge Cantu with capital murder, told the newspaper 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 Cantu's photo three separate times.

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. Burglars had recently struck, so they were guarding the home, located across the street from the trailer where Cantu lived.

Both were awoken by a pair of teenagers demanding money. The older of the two carried a .22-caliber rifle. Gomez was killed; Moreno was shot but survived.

Afterward, Moreno described his attackers as two Mexican-Americans he thought lived nearby.

After a South San Antonio High School teacher mentioned that students were saying Cantu had done the killing, police showed Moreno photos of five Hispanic men, including Cantu. Moreno, however, did not identify Cantu as his attacker and the case appeared closed.

About four months later, Cantu was involved in a bar shooting that injured an off-duty police officer. Cantu said the shooting erupted over a pool game and that he fired only when the officer flashed a gun and threatened him. The officer later said Cantu shot him four times in an unprovoked attack.

That case against Cantu was dropped.

"There was an overreaction, and some of the evidence may have been tainted. It could not be prosecuted," said former homicide Sgt. Bill Ewell, who oversaw the investigation.

Ewell, a friend of the officer, said the bar shooting prompted him to reopen the Gomez murder case.

He sent a bilingual homicide detective to show Cantu's photo to Moreno for the second time. Moreno still did not identify Cantu.

The next day, Ewell sent out a different bilingual detective who brought Moreno, who was then an illegal immigrant, back to the police station. Moreno was again shown Cantu's photo along with four others. The officer's report indicates that Moreno picked out Cantu, then signed and dated the back of the photo.

But the photo submitted into evidence at trial was not dated on the back, according to trial transcripts. Moreno said he felt compelled to do what police wanted, even though he knew it was wrong.

"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."