Although unlikely, 10-month-old Poseidyn Hemopo-Pickering's head injuries could possibly have been caused by a fall from his mother's arms in the days prior to his death, a Sydney-based forensic pathologist said today as testimony wrapped up at the murder trial for the child's father. 

Professor Johan Duflou was one of two witnesses called as lawyers for Anthony Pickering who spent the morning presenting their case in the High Court at Auckland. 

"I think it's a possibility [the child's injuries were accidental] but it's not one I necessarily favour as the most likely scenario," Dufou testified. 

Pickering, 32, who goes by his middle name Simon, opted not to testify on his own behalf, defence lawyer Ina Stewart pointed out during her opening. 

"Mr Pickering's position has not changed at all in the two years that have passed," Stewart said of the baby's September 2020 death at Starship Hospital after emergency responders found him unresponsive at his Manurewa home. 

Calling the boy's father to the witness stand, she told jurors, would add nothing of value to the three previous statements he gave police. 

"Simon Pickering did not cause these injuries," she said. "He does not know who or what did cause those injuries...You will not be hearing again from Mr Pickering because there's nothing more he can tell you." 

Prosecutors allege baby Poseidyn received head injuries so severe they could only be incurred through non-accidental trauma. They appear to have occurred during a 16-minute period on September 5 when Pickering was alone with Poseidyn and his 2-year-old sister as their mother ran a quick errand, authorities have said. 

The mother returned home to find the children napping and was woken up later by the defendant telling her to call an ambulance, according to earlier testimony. 

A child's car seat sits the Manurewa driveway where 10-month-old Poseidyn Pickering was injured in 2020. (Photo / NZME)

But she had dropped the baby two days before his death, the defence has noted throughout the trial. 

Medical experts called by the Crown said the child's injuries could not have been caused by a simple fall from his mother's arms. Duflou, the pathologist called to testify for the defence, agreed today that such a scenario would be unlikely but insisted it was "entirely possible" nonetheless. 

Children have received fractured skulls from short falls in the past, and if the child twists during the fall it may increase the chance of serious injury, he testified. 

It's possible the fall from the mother's arms damaged the structural integrity of Poseidyn's skull, making a fall from the bed days later much more lethal than it would normally be, he agreed. It would be similar to cracking an egg, where the second impact needs to be less intense than the first, he explained. 

While he acknowledged "it's certainly more likely that these are inflicted injuries rather than accidentally sustained injuries", outlier scenarios do occur and there's no way to determine with certainty how Poseidyn received his injuries, he said. 

Defence lawyers Stewart and Quentin Duff also briefly called to testify clinical psychologist Nick Lascelles, who commented on the defendant's "emotional presentation". During interviews with police, Pickering was described as having an almost jovial demeanor despite his son's fatal injuries. 

Lascelles described the defendant's occasional laughter as a long-standing coping mechanism linked to his childhood - an attempt to erect a facade during stressful moments. 

Both sides have now closed, and final addresses for the trial are set to take place tomorrow.