Captain Rogelio Maynulet, 29, is charged with murdering the man on May 21 in an incident during which US troops near the central town of Kufa fired at a civilian vehicle suspected of containing militia forces.

Nine witnesses were due to be heard Wednesday in the pre-trial hearing, known as an Article 32 investigation.

Members of media were ordered to leave the hearing, led by US investigating officer Michael J. Fadden, while the first witness, a neurosurgeon, gave testimony.

Maynulet was accompanied by his wife, also a member of the military, who put her hand on his shoulder and talked quietly with him as proceedings got under way.

The US military's Article 32 inquiry is the equivalent of a grand jury hearing and could initiate a court martial and, in this case, could lead to a life sentence.

Three days of hearings have been scheduled until Friday, after which Fadden will make a recommendation on whether any court martial should go ahead.

The hearing originally began in Baghdad on June 25 but was postponed while Maynulet's 1st Armoured Division returned to Germany.

A second session was held at the Pioneer Barracks in Hanau, near Frankfurt, western Germany on July 28 but it was also adjourned until all the witnesses could attend.

Maynulet has denied charges of murder and dereliction of duty for the killing of a follower of Moqtada Sadr, the radical cleric whose militia has been involved in protracted battles with the US-led forces occupying Iraq.

He is one of only a few US soldiers to face such charges.

According to an army statement: "A chase began and US forces shot at the vehicle. The driver and a passenger were wounded. Shortly thereafter, the wounded driver was shot and killed at close range."