The trial of a man accused of killing a three-year-old boy has been told the absence of a precise time of death is crucial to the case.
Liam Whoriskey (25), of Glenabbey Gardens in Derry, denies murdering Kayden McGuinness in 2017.
The toddler was found dead in his family home at Colmcille Court in the Bogside on September 17.
The defendant also denies two charges of child cruelty and one charge of failing to protect Kayden.
Professor Al-Sarraj, a consultant neuropathologist at King’s College Hospital in London, told Derry Crown Court the fatal non-accidental brain injury was likely to have occurred between 7pm on September 16 and 10am the following day.
He told the court the absence of a precise time of death was “most important in this case because it has restricted the number of options open to the court”.
The court has previously heard a post-mortem examination revealed Kayden had sustained multiple injuries and bruising.
There were at least 15 non-accidental bruises to the child’s scalp, which had been caused by blunt force trauma to the head.
The defendant had been babysitting the child and a five-month-old baby girl when their mother and his former fiancee, Erin McLaughlin, had stayed out overnight after socialising with family and friends.
Prof. Al-Sarraj said the head injuries sustained by the child were either minor or mild injuries and the bruising of the child’s brain could have been caused by someone squeezing the boy’s head.
Under cross-examination by a defence barrister, Prof. Al-Sarraj said he was not aware the child had displayed unusual behaviour on the evening before his death.
Ciaran Mallon QC said Kayden had gone to bed by himself, had not brought his toys to bed with him and did not play countdown with his mother after she had put his bedtime milk bottle into the microwave.
Asked if the unusual behavioural pattern could be an indication of the onset of swelling to the brain from an earlier injury, Prof. Al-Sarraj said he agreed with that possibility.
He said that, in such circumstances, a child would be confused, irritable and difficult to feed “in a manner typical of a child having sustained a head injury”.
The trial continues.