Leonard Nattrass-Berquist and Beauen Wallace-Loretz are on trial at the High Court in Auckland where they have denied murdering Ihaia Gillman-Harris in December 2014. Both were 17 at the time.
Today psychologist Sabine Visser told the court that she had 24 sessions with Mr Nattrass-Berquist.
She told the court Mr Nattrass-Berquist was still an adolecent, an age when typical behaviour could include being impulsive and aggressive. She said adolscents also had an inability to think about the wider consequences of their actions.
She said when she initially talked to Mr Nattrass Berquist about what happened inside the unit at the Epsom Ascot motel, there were gaps in his memory and he would withdraw and look at the floor.
Mr Nattrass-Berquist, who has been giving evidence in his own defence, said he was sexually assaulted by Mr Gillman-Harris and that Mr Wallace-Loretz came to his rescue, striking Mr Gillman-Harris over the head with a bottle of alcohol.
Ms Visser said in that situation, Mr Nattrass-Berquist would have been frightened.
She confirmed to Crown prosecutor David Johnstone that she did not ask Mr Nattrass-Berquist about text messages he sent to Mr Wallace-Loretz shortly before Mr Gillman-Harris' death.
The Crown says the text messages show the teenagers planning a violent robbery of Mr Gillman-Harris.
Ms Visser said she relied on what Mr Nattrass-Berquist told her and what she observed in her office to make her findings.
She confirmed to Justice Toogood that it was not part of her brief to discover if Mr Nattrass-Berquist was telling the truth.
Mr Nattrass-Berquist told the court he found out Mr Gillman-Harris had died the day after the fatal attack, and that he and his friend were moved from house to house by adults as police searched for him in relation to the fatal bashing.
Under cross-examination by the Crown prosecutor David Johnstone, Mr Nattrass-Berquist confirmed there had been a violent assault in the motel.
Mr Johnstone put it to him that he and his co-accused had planned the robbery and carried it out.
Mr Nattrass-Berquist denied that was the case, and said he was sad about what had happened.
He wept as he recalled calling his mother and telling her what had happened a day before handing himself into the police.