NASHVILLE, Tenn. -- Prosecutors said in opening arguments that a former attorney accused of killing his wife told a fellow prison inmate that he killed her with a wrench after she accused him of cheating on her.

LIVE STREAM: MARCH MURDER TRIAL

The claim was one of several new pieces of information revealed to jurors on Wednesday, the first day of the trial for Perry March, charged with second-degree murder in the death of Janet Levine March.

SPECIAL SECTION: March Murder Trial

The inmate, Cornelius King, testified that March confided in him while in prison. King said that March told him that he and Janet had a physical altercation after she found out he was cheating on her. King testified that March told him he hit her over the head with a wrench.

March was identified as a suspect soon after his wife disappeared in August 1996 but wasn't charged in the case until last year.

But his defense attorneys questioned the credibility of inmates, some of whom are testifying in exchange for lighter prison sentences on their own crimes.

The defense had its own trouble with inmate testimony Wednesday, after it unsuccessfully argued to delay the trial by introducing evidence of a confession by another man to the murder.

Defense attorney William Massey said a letter delivered Monday was from inmate Barry Armistead, who claimed to have had an affair with Janet March, a Nashville artist and socialite.

Massey said Armistead's letter said he and Janet March left town together about the time that the defendant claimed his wife left home saying she needed a vacation. The letter said Armistead and Janet March had a fight, she took sleeping pills while drinking and he later found her dead.

But when Armistead was questioned Wednesday by prosecution and defense attorneys, he denied writing the letter. The prosecution said Armistead, who has been in prison since 1997 on unrelated crimes, has earlier claimed to have different roles in the case.

Criminal Court Judge Steve Dozier declined a defense request to delay the trial, noting that a jury from Chattanooga selected to hear the high-profile case has been sequestered.

Because of the prominence of Perry and Janet March and the mystery surrounding her death, the trial has shaped up as one of the most high-profile in Nashville history.