One of the children of Lu Na McKinney whose husband is accused of murdering her during a family boating holiday four years ago, blamed themselves for her death, Dungannon Crown Court heard.

On Tuesday, the jury of eight men and four women also learned the youngster thought their 35-year-old mum had committed suicide because of an argument they had "over a pack of crisps" the evening before her death.

Details of the child's distorted thinking were given by a friend of Stephen McKinney who had told her of the affect the death of their mother was having on his two children.

She also told that court this was one of the reasons given to her by 44-year-old McKinney for denying police access to the youngsters for questioning them about what happened prior to their mum's death on Lower Lough Erne in April 2017.

McKinney originally from Strabane, but who lived with wife and children in Convoy, Co Donegal, and now with an address in Castletown Square, Fintona, Tyrone, denies murdering his wife during the boating holiday as a treat for their children and to celebrate their up and coming 14th wedding anniversary.

The court heard McKinney told his friend that he was "going to stop the police" talking to his children "as one of them was severely distressed" and thought their mother had committed suicide.

The woman said McKinney told her this was because they'd had "a row over a bag of crisps", that Lu Na had eaten the youngster's crisp earlier that evening before the children went to bed at the front of the hire cruiser.

Later under cross examination by defence QC Martin O'Rourke, she accepted McKinney told her police wanted to interview the children and that "one of them was blaming themselves because they thought their mother had committed suicide over an argument of a pack of crisps.

"And that he (McKinney) did not want to put the child through any police inquiry about what happened on the boat".

However, earlier she told prosecution lawyer Michael Chambers, McKinney "blamed himself" for Lu Na's death, "for not being able to pull her up, or get her out of the water". And this may have been due to a "major operation" he had earlier that year.

She said he thought that if he hadn't undergone the op, "he might have had the strength to get her out of the water". Asked if she'd told him "not to blame himself", she replied: "yes absolutely".

During their telephone conversations, sometimes two or three times a week, if not more, she said McKinney told her that Lu Na, despite his reassurances, went to check on the mooring ropes and as he went to join her, "he heard a splash.. just a splash" and that he tried to save her.

"He ended up in the water and he had a hand on the boat and she was pulling him down, then they both went down and he lost her and got back up himself .... he had to let her go to save himself or he would have drowned as well," the woman said McKinney told her.

She added Mr. McKinney described himself at the time as being "exhausted and tired" that he lost all sense of time and when police recovered Lu Na from the lough, "he was sick he could not find her himself or could not reach her".

The court also heard that Mr. McKinney was arrested in front of his children by police outside a Spar shop at Newbuildings, and looked "shocked" when told it was on "suspicion of murder".

Police also noted he was "shaking uncontrollably ... pale ... and repeated he didn't understand" and asked and was to happen to his children. Eventually his parent were contacted and the children left in the care of their grandparents.

One officer said while en route to Omagh police station he'd asked if he was on any medication, and was told "sleeping tablets" and admitted they had been ordered "on the internet".

Later a forensic toxicology expert said she'd analysed several beer cans taken from the hire cruiser for drugs, but found none. She said she also examined a sample taken from Mrs. McKinney and found a concentration of 0.18 mg of the drug Zopicone, per 1 litre of blood.

She told prosecution QC Richard Weir the drug was used as a sleeping aid for insomnia and "the level detected within the blood sample attributed to Mrs. McKinney was slightly ahead of the therapeutic range .. which was slightly below 0.1".

The court heard the general effects associated with Zopicon were depressive, it would encourage sleep, dizziness, a lack of balance, a temporary reduction in alertness and coordination. However these effects may be reduced given a past regular use of the drug.

Later under cross-examination she accepted she'd attended a high level meeting with police, prosecution and other experts in November 2018, but could not recall saying the effect,on Mrs. McKinney given the level detected "is easily described as sleepy".

The expert said she also did not recall saying it would also depend on a number of different factors and could not be specific as to how it may have affected her.

At hearing.