Dentist Colin Howell tried to trick psychiatrists into thinking he killed his wife on the spur of the moment in order to get a shorter sentence, he told the trial of his former lover Hazel Stewart.
The one time lay preacher, who went on to murder Ms Stewart's policeman husband Trevor Buchanan, said he told police his decision to murder his wife Lesley was spontaneous in the hope of convincing medics to support a plea of manslaughter on the grounds of diminished responsibility.
Howell gave this version of events to detectives inside prison two years ago - five months after he had confessed to the May 1991 killings - but he has since pleaded guilty to murder charges and claimed the deaths were extensively planned in conjunction with Ms Stewart.
Giving evidence for a fourth day, Howell also told Coleraine Crown Court he now remembered another planning meeting with Ms Stewart - he originally claimed there had been only one - in the days before the killings.
Ms Stewart, 47, from Ballystrone Road, Coleraine, denies being part of a joint enterprise with Howell to murder their spouses.
Her defence barrister, Paul Ramsey QC, put it to Howell, who has been sentenced to 21 years, there was no plot and that his June 2009 interview with police clearly indicated that.
But the father of 11, dressed in a grey suit, told the jury the account he gave to detectives was manufactured.
‘I began to deceive myself and even believed this was a spontaneous act that day.
‘I was beginning to lie again, beginning to see that if I could get it to be believed this was a spontaneous act that day psychiatrists would support a psychiatric plea and I would get less time in prison,’ he said.
Howell said when he originally admitted to church elders - as part of a religious confession - to gassing his wife and Mr Buchanan and staging it to look like suicide he intended to take responsibility for his actions.
But he said the mental impact of his second wife leaving him upon his imprisonment led him to consider a manslaughter plea.
Howell admitted murders after losing savings
Mr Howell believed he would land £20m by ploughing his life savings into a diving project to find Japan's war gold but ended up with only a few silver coins worth £30, the trial of his lover heard.
The dentist invested £350,000 in the recovery dig in caves in the Philippines only to discover it was a massive scam that only recovered a few brass ammunition boxes.
He told Coleraine Crown Court the realisation that he had been duped at the end of 2008 was the trigger which led to him confessing.
‘I made a decision in that moment that I wanted to confess to those murders,’ he said.
Howell had been persuaded to get involved in the ill-fated venture by a fellow Baptist and the man who presented him with the ammunition boxes containing the near worthless contents when he flew to Manila was a Christian.
‘I looked at him and said 'you're lying, you're a fraud', and as soon as I said that it reflected back on me and I knew I was a fraud too,’ he said.
Since the end of World War Two, tales have abounded that Admiral Isoroku Yamamoto, the commander-in-chief of the Imperial Japanese Navy, buried a multimillion-pound horde of gold bullion in bunkers in the Philippines.
The legend has prompted countless treasure hunts but none have struck the jackpot.
Paul Ramsey QC, Hazel Stewart's defence barrister, speculated that Howell would not have admitted to the murders had his ship come in.
‘If those ammunition boxes were packed to the gunnels with Yamamoto's gold would you have gone to the police?’ he said.
The lawyer, who has claimed the murders were motivated by money and not his desire to be with Ms Stewart, suggested his confession was also linked to his finances.
‘The reason you went to police was because you had no money left,’ he said.
Howell said it was not the loss of his savings, but the deception by someone who claimed to be a Christian believer that made him unburden his secret.
‘My conscience that had been buried deep in my own bunker covered with concrete suddenly exploded,’ he said.
