Retired FBI agent Thomas Michael Martens wept in the stand as he said he repeatedly struck his Irish son-in-law with a metal baseball bat over the head.
Mr Martens said he feared for his life and the life of his daughter Molly Martens Corbett.
They claim Mr. Corbett was choking Molly and threatening to kill her, and they acted in self-defence.
Both deny the second degree murder of Limerick man Jason Corbett in North Carolina two years ago.
Southern Correspondent with the Irish Independent Ralph Riegel is covering the murder trial in Lexington, North Carolina.
He says Mr.Martens made no secret of the fact he didn't like his son in law Jason Corbett:
It's expected Judge David Lee will put the jury in charge to consider a verdict on Monday evening or on Tuesday.
