SAN ANTONIO -- A Central Texas crime investigation shows the woman who says she shot boxer Tony Ayala Jr. during a reported break-in did not have detectable gunpowder residue on her hands, prompting a defense attorney to question the credibility of the witness.

The investigation by the Bexar County medical examiner's office suggests that Nancy Gomez may not have fired the shot that injured the prizefighter in the shoulder last December.

Investigators did, however, find gunpowder residue on the right hand of another woman who was in the house when Ayala is accused of breaking in with the intention of sexual assaulting Gomez, 18, and the second woman, Sandra Gutierrez.

"It's not just testimony, but rather, scientific evidence that is throwing off the credibility of (the women's) story," defense attorney Jimmy Parks told the San Antonio Express-News in Friday's editions. "It's another issue that will be looked at critically at the trial."

Ayala was indicted in the Dec. 12 break-in of the west-side home, which ended when he was shot. Ayala, a top junior middleweight contender in the early 1980s, was trying to make a comeback at the time.

Gomez had told police she awakened Gutierrez, who confronted Ayala with a .45-caliber gun and then handed the weapon to Gomez. The report states Gomez shot Ayala in the shoulder when he started to approach her.

A prosecutor downplayed the laboratory findings, saying the women are not on trial.

"We are aware of it and are unconcerned about it," First Assistant District Attorney Michael Bernard said Thursday.

Ayala, a convicted rapist, faces trial on charges of burglary with intent to commit sexual assault. If convicted again, he could get life in prison.

The trial, which has been postponed three times to allow his attorney to attend to his hospitalized father, is set to start Monday with jury selection.

Ayala won his first 22 fights and was headed for his first junior middleweight title bout in 1983. Instead, he got drunk and stoned on New Year's Day and raped a neighbor. He was sentenced to 35 years in prison and released in April 1999.

The boxer returned to his hometown of San Antonio to resume his career.