Colin Howell had a furious row with his brother-in-law over claims that he was deliberately drugging his wife so that he could have late-night trysts with his lover, Hazel Stewart, a court has heard.
Just after the death of her father, Harry Clarke, Howell had been with his wife Lesley and her brother Chris Clarke, who alleged he was feeding tablets to his sister.
It was on a night when Mrs Howell became drunk very quickly, Howell said.
But in Coleraine Crown Court yesterday, the dentist denied there had been any confrontation.
He told the jury: "I did not tell him I was giving her tablets. He made that up."
Howell confirmed to the jury how he would leave the house in the middle of the night to have sex with Ms Stewart when her husband, Trevor Buchanan, was away on police duties.
He said Mrs Howell would have taken red wine and temazepam to help her get to sleep, claiming it was part of a pattern that had developed when he and Ms Stewart would meet up.
He said she would open the back window of her house and let him in after they first made telephone contact.
Howell admitted that it meant his four children, Matthew, then aged six, Lauren, four, one-year-old Daniel and baby Jonathan, only months old, would have been left on their own. He denied blocking their bedroom door.
Howell said that he had access to temazepam and Mrs Howell had asked for the tablets. He said he gave her some in a bottle which contained 20 or 30, insisting she had wanted them.
He said Mrs Howell was a registered nurse who knew how to medicate herself. He said he gave her the temazepam, but did not force her to take them or put them into her mouth.
The judge, Mr Justice Anthony Hart, asked him: "Were you physically administering drugs to your wife?"
Howell replied: "Absolutely no."