KILLER dentist Colin Howell told his former lover's double murder trial yesterday how she vowed to kill herself if she thought she'd be caught.
An emotional Howell (51, right), who has already pleaded guilty to killing his wife Lesley and Trevor Buchanan -- the policeman husband of his then mistress Hazel Stewart -- wept when asked to tell the jury at Coleraine Crown Court when he and Lesley's four children were born.
Ms Stewart, who is accused of the double murder in May 1991, sat impassively in the dock as her ex-boyfriend explained why he had confessed to the crimes -- which he originally staged to look like a suicide pact -- 18 years later.
Taking the stand at the trial of the mother of two, Howell also said he could not have committed the crimes without Ms Stewart's help.
He said Ms Stewart panicked about whether they would get away with murdering Mr Buchanan and Ms Howell and making it look like suicide.
Howell told the jury he put the plan to her when they met in her car on an isolated road a week before the murder in May 1991.
"I remember the word crazy being used by her, that it's not going to work," he said. "That was the nature of the objection Hazel gave to me."
He said her concern was over being caught, not the concept.
"I remember her saying 'if I get caught I will slit my wrists before they come to get me'."
Howell said that when he phoned Ms Stewart again on the day of the killing she was panicking, but was having no second thoughts about the crime.
Howell's plan would see him poison his wife Lesley with carbon monoxide piped from his car into the family home before driving to the Buchanans' house to kill Trevor Buchanan in the same way.
He said that in order for it to work Ms Stewart had to agree to do four things: drug her husband with tablets ahead of his (Howell's) arrival; make sure her car was out of the garage so he could drive in with his wife's body in the boot; set out a pile of clothes to dress Mr Buchanan in after Howell killed him; cut up and burn the hosepipe Howell used to pipe gas into the policeman's bedroom.
Howell said he gave Ms Stewart the tablets -- sedatives used by his mother -- on the night he first put the plan to her in the car.
"When she took the tablets and put them in her bag I felt that was the moment the plan was agreed upon; it was almost as if a contract had been signed," he said.
Howell later claimed he could not have carried out the murders if Ms Stewart had not done what he requested.
"It couldn't have happened without her doing everything I asked her to do," he said.
The bodies of Ms Howell (31) and Mr Buchanan (32) were found in a fume-filled garage in the seaside town of Castlerock.
Howell, who is serving a 21-year sentence at Maghaberry Prison, Co Antrim, had poisoned them as they slept in their own homes then set up a scene to look as though they had taken their own lives, because they could not cope with his and Ms Stewart's affair.
Ms Stewart (47), from Ballystrone Road, Coleraine, denies the murder charges.
Howell broke down a number of times while giving evidence. On one occasion he offered an explanation to the court: "Obviously I've done a terrible thing and it's difficult."
The trial also heard how the couple started having secret sex again just six weeks after the murders.