JOINT BASE LEWIS-MCCHORD, Wash. — Members of an American Army unit consumed with drug use randomly chose Afghan civilians to kill and then failed to report the abuses out of fear they would suffer retaliation from their commander, according to testimony in military court here on Monday.

The testimony, in a hearing to determine whether one of those soldiers, Specialist Jeremy N. Morlock, would face a court-martial and a possible death sentence, came the same day that a videotape in the case was leaked showing Specialist Morlock talking to investigators about the killings in gruesome detail with no apparent emotion.

Top Army officials worry that the case against Specialist Morlock and four other soldiers accused in the killings of three Afghan civilians will undermine efforts to build relationships with Afghans in the war against the Taliban.

The soldiers are accused of possessing dismembered body parts, including fingers and a skull, and collecting photographs of dead Afghans. Some images show soldiers posing with the dead. As many as 70 images are believed to be in evidence.