Later, the inmate said Martin MacNeill opened up, and allegedly admitted murdering Michele MacNeill.
"He said that he gave her some Oxy and some sleeping pills and then got her into the bathtub," he said. "Later on, he just said he had to help her out… He said he held her head underwater for a little while."
At the time of the alleged conversation, Martin MacNeill was serving time at a federal prison in Texas for an identity fraud conviction. Inmate #1 said he met the man, who he referred to as "Doc," during a computer class at the prison.
Inmate #1 said he came forward to investigators with the information after Martin MacNeill was arrested on suspicion of murder.
"I made some wrong decisions and I'm just trying to do right," the inmate said.
Though the inmate was not offered anything in exchange for his testimony, defense attorney Randy Spencer grilled the man about comments he made to family members that testifying against Martin MacNeill would help him get out of prison early an effort he referred to as "Operation Utah."
The inmate said he was hopeful, but never asked for anything in exchange for his testimony.
Former Utah County jail inmate, Jason Poirier, who was incarcerated with Martin MacNeill in mid-December 2012, testified on Wednesday that the defendant also told him he had killed his wife.
Poirier said he started a conversation with Martin MacNeill about why MacNeill wore different shoes than the rest of the inmates.
"I can get away with a lot of things," Poirier recalled Martin MacNeill saying. "I'm getting away with murdering my wife."
Poirier said when he went to give his condolences to Martin MacNeill about his wife, that MacNeill told him not to worry and that, "I'm glad the bitch is dead."
Poirier said he later asked Martin MacNeill if he was being serious when he said he had killed Michele MacNeill.
"He said, 'Yes, I'm serious, I mean, look where I'm at,' " Poirier testified.
During cross-examination, defense attorney Randall Spencer attempted to discredit Poirier, pointing to Poirier's extensive criminal history and that Poirier hoped that informing on Martin MacNeill would help get his record expunged, but said he was only "helped a little bit."
He said he decided to come forward because, "I believe it is the moral thing to do."
Outside of court, Spencer called the inmate's testimony "not credible and self-serving" and "inaccurate at best."
Also Wednesday, Judge Derek Pullan denied a defense motion for a mistrial, after a media report about the trial suddenly blared from the laptop of prosecutors' paralegal.
But after listening carefully to the news clip, Pullan denied the motion, saying "it would have presented no new information" to the jury.
"Shut that off!" Pullan had ordered when the news clip began playing. "Who is that? Shut that off!"
Later, outside the presence of the jury, Pullan said that he spoke loudly and repeatedly in an effort to cover up the sound of the broadcast from the jury who are ordered to not to listen to or read any media reports about the case during the trial.
Pullan had said he only heard a newscaster refer to "Martin MacNeill" and "on trial for murder," but Spencer said he heard the report mention that MacNeill's wife was found in the bathtub. He accused prosecutors of misconduct, and motioned for a mistrial.
Prosecutors claim Martin MacNeill, 57, killed his wife in April 2007 in order to continue an extramarital affair with 37-year-old Gypsy Willis.
Martin MacNeill is accused of giving 50-year-old Michele MacNeill a toxic combination of prescription medications after she came home to recover from plastic surgery. However, the state medical examiner's office has never ruled the woman's death a homicide.
The defendant is charged with first-degree felony murder and second-degree felony obstruction of justice.
Michele MacNeill was found unconscious in her bathtub on April 11, 2007, by her 6-year-old daughter, Ada MacNeill.
The child was sent by her father to a neighbor's house to get help, and eventually Michele MacNeill was pulled from the bathtub by a neighbor and Martin MacNeill. The two attempted CPR before medical crews arrived.
Those medical crews also attempted to perform CPR and other life-saving efforts before Michele MacNeill was taken to an American Fork hospital, where she was pronounced dead.
After an autopsy in 2007, her manner of death was ruled "natural," the result of "chronic hypertension and myocarditis, which are capable of causing acute unexpected arrhythmia and sudden death."
But investigators say Martin MacNeill called the medical examiner multiple times and gave misleading information. In 2010, in a new investigative report, Chief Medical Examiner Todd Grey changed the cause of death to the combined effects of heart disease and drug toxicity. The manner of death was changed to "undetermined."