A farmer tried to hang himself when he was accused of murdering Nat Fraser's wife Arlene.
Hector Dick was already in jail for lying about a key piece of evidence when he was detained in connection with Mrs Fraser's disappearance.
When he was returned to his cell, Mr Dick, of Mosstowie, Elgin, tried to commit suicide, leaving a goodbye note for his wife.
The evidence came out as Mr Dick gave evidence for the fifth day at the trial of Fraser, accused of murdering his wife 14 years ago.
The mother-of-two disappeared from her Elgin home in April 1998 and her body has never been found.
The court heard that Mr Dick was jailed in 2001 for lying about a Ford Fiesta which police believed had played a part in Mrs Fraser's disappearance.
He attempted suicide in his cell at Porterfield Prison in Inverness.
On Wednesday defence counsel John Scott QC told Mr Dick that his suicide attempt less than 24 hours after being accused of murder could have been seen as a "sign of a guilty conscience".
The witness replied: "It was pointed out to me."
Mr Dick has already told the court that Fraser, 53, confessed to hiring a hitman to kill his wife, burning her body and scattering her ashes.
The jury also heard on Wednesday that Mr Dick told police in 1999 that he believed Fraser was involved in his wife's disappearance.
He said to officers: "As regards Nat Fraser, although he has never told me what he has done, my opinion is that he was involved in his wife's disappearance."
Fraser's defence lawyer, John Scott QC, challenged the witness about the fact the statement to police was different to what he has told the court about Fraser's "confession".
Mr Dick replied: "Nat told me various stories. I couldn't make up my mind which was right and which was wrong."
Asked if he should have told the police everything he knew, he replied: "I hadn't crossed that threshold yet."
Fraser denies attacking his wife between April 28 and May 7, 1998 at the home they once shared in Smith Street, New Elgin, or elsewhere in Scotland.
It is alleged he strangled her, or murdered her "by other means to the prosecutor unknown".
The indictment against Fraser says he knew Mrs Fraser had seen a solicitor about divorcing him and getting a cash pay-off.
Fraser has lodged papers in court claiming that on April 28, 1998, he left an address in Burnside Road, Lhanbryde, where he was staying, at about 7.30am and spent the day making van deliveries to hotels, restaurants and shops - pausing to make a phone call just after 9am.
The jury has heard that there has been an earlier trial in 2003 when Hector Dick had been one of three men accused of murdering Mrs Fraser, but had left the dock and given evidence for the prosecution. Another man on trial then, Glenn Lucas, was now dead. The third man was Fraser.
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