The 47-year-old, from the town, denies the charges and claims she lied about what had happened because she lived in fear of Howell, the jury has heard.  Howell’s relationship with Mrs Stewart continued after the murder of their partners for up to five years, the jury has heard.  But the court was told that Mrs Stewart was racked with “Christian guilt” about the extramarital affair.  Howell’s answer was to inject her with drugs to make her lose consciousness, the court was told.  On one occasion he feared he might have killed Mrs Stewart as well by giving her an overdose, the court was told.  Trevor McAuley, a fellow church member who went out with Mrs Stewart for several years after she eventually broke up with Howell, told the jury yesterday that she had occasionally spoken about the previous relationship.  He told the court: “He would administer the drug to her and she would pass out and she would really know nothing about it until the morning when she woke up.”  Asked why Howell did this, Mr McAuley said: “So he could enjoy sexual gratification with her without her feeling the guilt of it while he was able to have pleasure.”  He added: “I remember her saying what a nice feeling it was as she drifted off.”  But he went on: “On one occasion he almost overdid it and gave her too much and he was actually concerned if he was going to get her to come round again.”  Mr McAuley also recounted one occasion he had been at Mrs Stewart’s house late one night when he heard her scream and looked out the back to see Howell standing in the garden, which backed on to a forest.  “This was around 12 o’clock at night and he would have had to come through the forest, he would have had to come through brambles to get to the back fence,” he said  “I could see him standing motionless like a statue.”  He said that Mrs Stewart had stopped him from going out to confront Howell.  “She made a comment not to approach him because I didn’t know what he was capable of,” she added.  Earlier the court heard who church members secretly steamed open a letter from which Howell hinted that he had killed his wife but they did not think it suspicious.  Colin Howell wrote to his mistress, Hazel Buchanan, a few days after he had murdered his wife, Lesley, and her husband, Trevor Buchanan, saying “I taken a mother from her children”.  Howell gave the letter to a fellow member of a baptist church to pass to his mistress but the man steamed it open as evidence that the two were having an affair. The note was also given to the church's pastor.  But no-one passed the note to police, convinced that the two victims had committed suicide, Coleraine Crown Court in Northern Ireland heard.  Mrs Howell, 31, and Mr Buchanan, 32, were found dead in a car filled with carbon monoxide fumes in Castelrock, Co Londonderry, on Sunday May 19 1991.  Police were convinced the pair had taken their own lives after hearing how Colin Howell and Mrs Buchanan - both apparently devout members of the local Baptist church in nearby Coleraine - had been having an affair.  But almost 20 years later Howell dramatically confessed that he had gassed them both in their sleep and faked the suicide scene so that he and his lover could be together.  Howell was jailed for life last year but Mrs Buchanan – who has remarried and is now known as Hazel Stewart – is on trial for the two murders.  Mrs Stewart, now 47 and from Coleraine, denies the charges.  The jury heard how some friends had raised suspicions about the circumstances of Mrs Howell and Mr Buchanan’s deaths to police at the time but the case was never treated as a murder investigation.  Derek McAuley, another member of the congregation, told the jury how, on the day of the two victims’ funerals, Howell handed him a note and asked him to pass it to his mistress, whom he had forbidden from seeing by church elders.  He said that he did so but not before secretly steaming the envelope open and photocopying the letter as evidence that the affair was still going on.  It was then passed on to the pastor, the Revd John Hansford, he told the jury.  The letter spoke of the possibility of Howell and his mistress resuming their affair despite the disapproval of the church and even leaving the town to start a new life together.  In a tantalising reference to the murders, Howell added: “I have taken a mother from her children but God will provide another for them.  “I only hope and pray it will be you.”  Paul Ramsay QC, defending Stewart, asked: “It didn’t occur to you that this line in the letter might have been of interest to the police?”  Mr McAuley replied: “No, I thought it was because of the affair.”
A dentist who murdered his wife and his lover&rsquo;s husband so that he could be   with his mistress used to drug her to take away her &ldquo;guilt&rdquo; while they were   having sex, a court heard.