Former champion kickboxer Adam Watt had enough mental capacity after he was bashed with a sandwich press to attend most of the trial of a corrupt cop whose case he believed was intrinsic to the charges against him, a court has heard.

Mr Watt, who was known as "the Aussie sniper" in his kickboxing career, was on remand for conspiring to import pseudoephedrine into Australia when another inmate clobbered him with a sandwich press concealed within a pillow slip in October 2009.

The attack left him clinically dead before he mounted a recovery.

He is suing the state for breaching its duty of care, claiming that the attack at Silverwater Prison left him with permanent injuries that could have been prevented if the notoriously violent offender who inflicted them had been properly supervised.