A former South Dakota National Guardsman who suffered post traumatic stress after he got back from the Iraq war claims he acted in self defense when he killed a man five years ago.

James Gregg of Harrold was convicted of second-degree murder in 2005 for shooting James Fallis in the back five times. Gregg wants a new trial because he says jurors in his first trial never got to hear testimony about Fallis' violent past. 

Gregg says he shot and killed Fallis because he feared for his life when the two got into a fight on the Crow Creek Indian reservation back in July of 2004.

"I've never been so scared in my life. This was something over the top, even more than I experienced in Iraq," Gregg testified in federal court. 

Gregg says Fallis had a long history of violence, including an incident in June of 1999 where Fallis tried hitting his cousin with a large tire iron.  A wildlife officer had to draw his gun on Fallis to get him to put the weapon down.

None of that testimony or other fights Fallis got into were allowed at Gregg's first trial.

His defense lawyers argue jurors should have heard about Fallis' violent past, because it shows why Gregg feared him in the first place.

But prosecutors say Fallis' past had nothing to do with the shooting and the judge made the right decision in not allowing it in his first trial. They even said Fallis and Gregg were good friends.

But Gregg testified Tuesday in federal court day they weren't good friends.  

"I wanted to stay on his good side because he could be a very violent person at times.  My dad always warned me to stay away from him," Gregg said in court. 

Gregg says when he and Fallis got into a fight, he thought Fallis was going to his vehicle to get a gun. And that's why he shot him.

Gregg is currently serving a 21 year sentence. The federal judge in the case will decide whether Gregg will get a new trial at a later date.