Lawyers for Sgt. Adam Holcomb of Youngstown, Ohio, said during court-martial proceedings that Chinese-American Danny Chen, 19, was tormented by his family's actions, which Chen's mother denied Tuesday, the Fayetteville (N.C.) Observer reported.
Defense lawyers also argued that Chen failed as a soldier and an infantryman who was punished frequently so he and others would be safe.
Prosecutors had described Chen as an Army private who had difficulty adjusting to a new unit because of verbal and physical abuse.
Prosecutors also said Chen's apparent suicide exemplified the failure by his superiors to curb hazing and protect a young soldier in a combat zone. Chen, of New York, was found dead in a guard tower in Afghanistan's Kandahar province last October.
Holcomb is the first of eight soldiers to be tried in Chen's death, the Observer said.
Suicide "was the only way he could think of to make the abuse stop," said Capt. Blake Doughty, a prosecutor.
But Capt. Dennis Hernon said Holcomb, who was Chen's roommate, never hazed the soldier.
"There's one and only one person responsible for the death of Pvt. Danny Chen," Hernon said. "That person is not Sgt. Holcomb. That person is Danny Chen."
Hernon said Chen told soldiers at Fort Wainwright, Alaska, his family disowned him.
Chen's mother, Su Zhen Chen, testifying through an interpreter, said she had a good relationship with her son and was shocked by his death, the Los Angeles Times reported.
She denied that she and her husband had ever disowned their son, testifying they had a close relationship with him. She said she and her husband were disappointed when their son joined the Army instead of going to college, but that they were proud of his service.
"He's my only son," she said. "Why would I disown my only son?"