The NSW Supreme Court murder trial of Mason John Hucker, 25, came to a close in Dubbo when the accused made a plea bargain with the Crown.

Mr Hucker was convicted of the manslaughter of Kenneth James Hutchings, which happened in March last year.

The court heard Mr Hutchings, his father Ray Hutchings and Mr Hucker embarked on a hunting trip on March 16 on a property near Condobolin.

Crown Prosecutor Peter Barnett told the court the trio had only one gun and were shooting kangaroos and pigs from the accused's ute.

"The accused was doing most of the shooting and the deceased and his father were going out and getting most of the carcasses," he said.

On the day of the shooting the group had set out towards Euabalong and had a number of kangaroos on the ute when they "consumed some marijuana".

"At 4am the accused shot a roo about 75 yards from the ute," Mr Barnett said. "The deceased walked over to the roo while the accused reloaded the gun and aimed out the window and fired at the deceased."

When Mr Hutchings senior asked, "what are you doing?" the accused replied that the victim had raped his mother, his sister and his grandmother.

Mr Hutchings junior died from a gunshot wound to the lower stomach.

During the course of the trial, forensic psychiatrist Dr Hugh Jolly told the court Mr Hucker suffered from paranoid schizophrenia.

"I am of the belief he has an abnormality of mind stemming from an underlying condition," Dr Jolly said. "He's unable to understand that his beliefs (at the time of the shooting) were actually not correct."

At yesterday's sitting, Judge Rod Howie thanked the jury for their service before dismissing them. "It is not unusual for the parties to come to an acceptance of what the end result of the trial should be," he said.

"Why should a person who kills another person while under the influence of a mental illness...be treated as a cold, deliberate murderer?

"Mr Hucker was afflicted with an appalling psychiatric illness and the deceased lost his life for no apparent reason (but) he is not a murderer and should not be treated as such."

Mr Hucker's sentencing hearing starts Monday.

in Dubbo and he will be sentenced later that week.

Mr Hucker sat quietly during yesterday's proceedings, as he had for most of the trial and kept his head down after Justice Howie formally convicted him of the charge.