Bales, an Ohio native and father of two from Lake Tapps, Washington, faces 16 counts of premeditated murder and six counts of attempted murder over the attack.
Prosecutors say that Bales wore a T-shirt, cape and night-vision goggles — no body armor — when he slipped away from his remote post at Camp Belambay.
In between attacks he woke a fellow soldier, reported what he had done and said he was headed out to kill more, the soldier testified. However, the other soldier did not believe what Bales had said and went back to sleep.
Eleven of the victims were from the same family.
On Thursday, a US Army DNA expert testified that Bales had the blood of at least four people on his clothes and guns when he surrendered.
The blood of two males and two females was discovered on Bales’ pants, shirt, gloves, rifle and other items, said Christine Trapolsi, an examiner at the army’s Criminal Investigation Laboratory.
To preserve the evidence, she said she only tested a portion of the bloodstains and it is possible that more DNA profiles could be discovered through additional testing.
Bales has not entered a plea and was not expected to testify. His attorneys have not discussed the evidence but say Bales has post-traumatic stress disorder and suffered a concussive head injury during a prior deployment to Iraq.
A US agent who investigated the massacre has testified that local villagers were so angered it was weeks before US forces could visit the crime scenes about a kilometer from a remote base.
By that time, the bodies had been buried and some bloodstains had been scraped from the walls, the agent said. Other stains remained on walls and floors.
Investigators recovered shell casings consistent with the weapons Bales reportedly carried. They also said Bales tested positive for steroids three days after the killings.