A jury will decide whether a boat owner who claimed a "drug crime syndicate" and Queensland police were involved in a fatal marine incident is of sound mind.
Stan Anthoulas, 54, told the District Court on Monday he received death threats, was "followed by cars" and evaded a "predatory group" before the February 2016 Brisbane River tragedy that claimed a woman's life.
Crown prosecutor Danny Boyle has since called on forensic psychiatrist Russ Scott to give evidence regarding the mental health of Anthoulas, who is representing himself.
"His (Anthoulas') default position ... is that 'it is all a conspiracy against me, the evidence has been fabricated ... there are corrupt police giving false evidence, the police may be involved in organised crime'," Dr Scott told the jury on Thursday.
"All of those things, those belief systems, impact on Mr Anthoulas' ability to present a coherent and externally consistent defence.
"We have seen from the (court) transcripts there are a number of times where suddenly something will occur to him and he will interject with that when it is ... not relevant ... but also is a product of his delusions."
The matter has been adjourned until Wednesday, when Dr Scott is expected to be cross examined by Anthoulas and more witnesses called.
The jury will then give a verdict on whether Anthoulas is of sound mind, which will determine how the trial - which is in its second week - will proceed.
Anthoulas gave evidence on Monday, saying he had been in a relationship with the woman who died on his boat but she was involved in the "wrong crowd" and had warned him "my life could be in danger".
He told the jury there were suspicious incidents in the lead-up to the boat sinking, along with death threats received.
Anthoulas also detailed an incident in which he claimed he had to evade a "predatory group" when he arrived to meet a friend at a Brisbane hotel before the tragedy.
When Judge Tony Moynihan asked on Monday what was the relevance of his claims, Anthoulas said: "I believe on that day of that boating incident ... there was a predatory group waiting, including police, and my boat was possibly swamped deliberately."
Anthoulas' vessel sank 50m off Murarrie as it queued up at a boat ramp returning from a fishing trip.
The woman died after she became trapped underneath the forward deck.
Anthoulas has pleaded not guilty to contravening the general safety obligation of a ship owner, causing death or grievous bodily harm.
