The American contractor, Raymond Davis, 36, shot dead two Pakistanis in the eastern city of Lahore on Jan. 27. He said he acted in self-defense and the United States says he has diplomatic immunity and should be repatriated.

The United States had retained a retired judge, Zahid Hussain Bokhari, who is also a former government prosecutor, to help with the Davis case.

“The court adjourned the hearing until March 8 because Mr.Bokhari said he needs time to complete papers for the case,” said Asad Manzoor Butt, a lawyer for the families of the two men Davis killed.

Davis last week filed a petition seeking immunity but Butt said the court did not entertain that request. The question of whether Davis enjoys immunity is being heard separately by the Lahore High Court.

Security was tight at Kot Lakhpat jail, where the trial is being held for security reasons. Machine guns were installed on top of water towers inside the jail and concrete barriers were placed on the road leading to it.

Davis, a former US special forces officer, has been charged with double-murder and faces possible execution.

There have been conflicting accounts about the identity of the two men Davis shot, with Davis and a police report indicating they were armed robbers while Pakistani media and some officials have portrayed them as innocent victims.

On March 14, the Lahore High Court will decide whether Davis has diplomatic immunity, another contentious issue that the government has said must be decided legally, at the risk of angering the United States and jeopardizing up to $3 billion a year in US military and civilian aid.

But with public anger and anti-American feeling running high, President Ali Asif Zardari’s unpopular government had little choice but to let the case go through the courts, analysts say.

In addition to causing a diplomatic standoff, the case has strained relations between the CIA and Pakistan’s main Inter-Services Intelligence (ISI) spy agency, which says it did not know of Davis’ presence in the country.

Relations between the spy agencies — which is seen as crucial to ending the almost decade-old war in neighboring Afghanistan — took a blow in December, when the CIA station chief in Islamabad was forced to leave the country after his name was published in a court filing over attacks in Pakistan by pilotless US aircraft.

The latest case has made things worse, as even the usually tight-lipped ISI noted.

“Post incident conduct of CIA has virtually put the partnership into question ... it is hard to predict if the relationship will ever reach the level at which it was prior to the Davis episode,” the ISI said in a letter to the Wall Street Journal last month.