U.S. Secretary of Defense Leon Panetta. Picture: Reuters/Kevin Lamarque

Washington: In the search for an explanation of why a US soldier left his base in Afghanistan at night and killed 16 civilians in their homes, some experts have raised the possibility that mental illness or a brain injury may have played a role in the massacre.

The staff sergeant, believed to be 38, could be executed if convicted.

Defence Secretary Leon Panetta said the suspect would be brought to justice under the US military legal code, which allows for the death penalty in some cases, in spite of Afghanistan’s demand that the man be tried in an Afghanistan court.

He is accused of breaking into village homes and opening fire, killing 16 people including women and children.

“Then at some point after that (he) came back to the forward operating base and basically turned himself in, told individuals what happened,” Panetta said on Monday.

Afghan President Hamid Karzai has described the shootings as “unforgivable”, and the Afghan parliament declared that “people are running out of patience” over the behaviour of the 130 000 US-led Nato troops deployed in the country.

The Taliban threatened to take revenge against “sick-minded American savages”.

A US official said the staff sergeant had suffered a traumatic brain injury in a vehicle rollover in 2010 in Iraq, was treated and returned to duty.

Experts caution against jumping to conclusions, but two facts are known. This was the sergeant’s first deployment in Afghanistan, but he had served three tours of duty in Iraq.

And the risk of mental illnesses such as post-traumatic stress disorder, depression and anxiety-related disorders is generally higher during subsequent deployments than during a soldier’s first.

“The more exposure there is to trauma, the worse it’s going to be,” said David Reiss, a psychiatrist who has treated patients with post-traumatic stress disorder.

The massacre is the latest serious test of the US-Afghan alliance as the two countries pursue difficult talks on securing a strategic pact to govern their partnership once foreign combat troops leave in 2014.

The weekend incident is the latest in a series of actions by troops that has provoked outrage in Afghanistan, and comes weeks after the burning of the Qur’ans sparked riots that killed 40 people and plunged ties to an all-time low.

There were no reports of protests by yesterday, and Kandahar community leaders appealed against any violence. – Sapa-AFP, Reuters