Stephen Long being sentenced in the Invercargill District Court today.

The family of a hunter who mistook his son for a deer and fatally shot him in the head clapped and sobbed as he was discharged without conviction today.

Stephen Phillip Long (61), of Invercargill, a manager for a lighting company, had earlier pleaded guilty to carelessly using a firearm causing the death of Samuel Phillip Long (24), while they were hunting on Stewart Island on March 23 this year.

Long quietly wept throughout most of his 80-minute sentencing in the Invercargill District Court today and gave a faint smile when Judge Bernadette Farnan announced he would not be convicted because of the unusual circumstances of the case.

They included Long's remorse, his good character, his 41-year experience as a hunter without any previous incidents or near misses, the significant impact a conviction would have on his family, his job, his finances and his ability to travel, and the "forever psychological handicap'' he would carry because of what he had done, she said.

His wife and three remaining children had urged her not to convict him and she had also taken that into consideration, Judge Farnan said.

After he left the dock, Long walked to the public gallery and gave his wife, Helen, a long hug before hugging other supporters.

He and his wife left the court room hand in hand.

Long declined to comment to waiting media.