FAIRBANKS -- Nathanial Kangas, accused of killing two Alaska State Troopers two years ago, opted Wednesday not to present a defense to charges of first- and second-degree murder.

Closing statements in the trial are expected Friday.

Kangas, 22, is accused of killing Sgt. Patrick "Scott" Johnson and Trooper Gabe Rich on May 1, 2014 in Tanana after his father, Arvin Kangas, resisted arrest on an assault charge.

Fairbanks District Attorney Gregg Olson wrapped up the case for the prosecution at about noon Wednesday following testimony by a trooper investigator that he had no doubt that Nathanial had done the shooting. The defense has admitted this, but defense attorney Greg Parvin said in his opening statement that it was an impulsive action, with no forethought.

After the prosecution concluded its case, Parvin rested his case and Kangas told Superior Court Judge Paul Lyle he would not testify.

Parvin did ask that three charges of tampering with physical evidence be dismissed, citing a lack of proof that he moved the troopers' weapons after their death and removed marijuana from the house.

Lyle declined to dismiss the tampering charges related to the weapons, saying that an expert witness testified to his belief that one person could not have "racked" the guns after their deaths. Kangas' father Arvin has been convicted of tampering with the weapons and is serving an eight-year jail term.