Joshua Josef Barker, 31, faced a seven-day trial in the Launceston Supreme Court after pleading not guilty to murdering Dale Watson and assaulting Timothy Bumford on March 9, 2018.

Barker mounted a kerb on the corner of Burrows and Knox streets and hit Mr Watson from behind, propelling his body 14 metres.

The incident happened a street away from where Barker was bashed by four men with blunt objects in June 2009.

Barker suffered delusions, paranoia, profuse sweats and lived in fear after the assault, which led to him being diagnosed with post-traumatic stress disorder.

A career medical officer told the court Barker was suffering from an acute phase of PTSD on the day Mr Watson was killed.

Defence and prosecution agreed Baker was suffering from a mental illness on March 9, but they differed in their views about the act he committed.

The elements underpinning both charges were explained to members of the jury and an alternative to murder was presented - manslaughter by culpable negligence.

Defence lawyer Evan Hughes asked the jury if they could rule out that Mr Barker's car was doing nothing more than driving inherently dangerous, with that failure to have reasonable care for other road users and pedestrians equating to the manslaughter verdict.

But Crown prosecutor Linda Mason successfully argued Barker murdered Mr Watson but he wasn't guilty of the act because he was insane at the time, with the jury returning a unanimous verdict after just 40 minutes on Tuesday afternoon.

Barker was also found to have assaulted Fastway Couriers driver Mr Bumford on the same day as the hit-run, but was again found not to be criminally liable by way of insanity.

Justice Robert Pearce remanded Barker to reappear on November 18.