AUBURN – A Sabattus man on Friday changed his plea from not guilty to not criminally responsible in the fatal shooting of his father at the older man’s 65th birthday party.

The plea paves the way for Scott Poirier, 34, to use an insanity defense in his trial, which is expected to get under way in September.

Police believe Poirier stood in his father’s yard and fired a rifle through a sliding glass door last Nov. 8. Roland Poirier was hit in the neck as he sat at a table celebrating his birthday with a roomful of family and friends.

Poirier told police he had been sexually abused by his father when he was younger and wanted to make sure it didn’t happen to his own young children, according to court documents.