A 54-year-old man who denied murdering his wife by stabbing her through the heart had admitted her manslaughter on the basis of diminished responsibility, a Caernarfon crown court jury heard.

Paul Jordan, of Ffordd Siabod, Felinheli, Gwynedd, a BT worker, killed Betty Jordan, 53, who he’d met in Ireland when they were in their teens, after selecting a knife from the kitchen at her home, the prosecution alleged.

Prosecuting QC Peter Griffiths claimed it was a case of murder. He said "obsessed" Jordan left his rented property at Felinheli and drove to the family home at Trem y Garnedd, Bangor, at the end of July, to rid himself of a perceived "problem."

He thought his wife was having an affair. "He intended to kill his wife and then in all probability kill himself," the QC remarked.

He went into the former matrimonial bedroom and stabbed his wife.

"We say this is a case of murder, not manslaughter," Mr Griffiths declared.

Defence QC Paul Reid in an opening address to the jury said a doctor felt Jordan had a severe mental illness. Just over a fortnight before the tragedy he had been referred to community mental health services.

The defendant’s belief his wife was having an affair never went away. Medical records referred to his "obsession and paranoia."

Mr Reid said the jury would also hear evidence that the defendant had been a heavy drinker, possibly an alcoholic, but he held down a responsible job despite this and had stopped drinking.

About a week before the killing of his wife, a good friend had committed suicide and Jordan "hit the bottle again."

The trial before Judge Rhys Rowlands continues.