Prosecutors in the first-degree murder trial of Pamela Phillips challenged the credibility of a defense witness on Monday.

Tucson-based doctor Lawrence D'Antonio was called to testify on behalf of Phillips because of his connection to a man who was known to have made threats against Gary Triano.

Phillips is on trial for first-degree murder and conspiracy to commit first-degree murder in the bombing death of her ex-husband Triano in 1996.

D'Antonio had been hired as a caretaker for a man named Neil McNeice who was an associate of Triano.

Phillips' defense team has said McNeice, now dead, made public threats against Triano after providing him an $80,000 loan in the mid-1990s. That loan, the defense argued, was secured through the collateral of what McNeice thought was a diamond ring. The ring, however, turned out to be cubic zirconia.

D'Antonio said he heard McNeice, whom he described as a longtime heroin addict, make numerous threats against Triano and others during their association.

Deputy Pima County Attorney Rick Unklesbay asked if D'Antonio ever warned Triano about the threats.

"I would never warn Gary Triano," D'Antonio said. "As far as I was concerned, he robbed a man of $80,000 and whatever happened to him was his problem."

Unklesbay asked whether it was ethical to not warn a man of a threat against his life.

"Does your hippocratic oath only apply to people you like?" Unklesbay said.

D'Antonio said the oath was not mandatory and that Triano was not his patient.

He also said he spoke with the FBI many times about McNeice's criminal activity. D'Antonio said he requested the FBI provide witness protection services for him in exchange for providing information about McNeice.

D'Antonio said he feared McNeice, McNeice's bodyguard and possible connections he had to Armenian organized crime.

Unklesbay also questioned the accuracy of D'Antonio's recollections of events from around the time of Triano's murder.

The trial continues today in Pima County Superior Court.

Contact reporter Patrick McNamara at 573-4241 or On Twitter @pm929.