Attorneys for an Army Reserve soldier on trial for murder in Georgia say he killed a superior because he was dehydrated and delirious from a crash diet after being ordered to lose weight.

Army Staff Sgt. Rashad Valmont's fiancée testified Wednesday that he quit eating and put in extra hours at the gym and sauna after being ordered by a supervisor to shed 3 percent of his body fat quickly. Two days later he walked into a different superior's office holding a Glock handgun, took aim and shot the man six times.

Valmont faces life in prison if convicted of military charges of premeditated murder in the June 2010 slaying of Master Sgt. Pedro Mercado at Fort Gillem near Atlanta.

A military psychiatrist testified she believes the soldier was delirious from dehydration and other effects of fasting.