The trial of five Sudanese accused of killing an American diplomat opened in Khartoum, the state news agency reported Sunday.
The official SUNA agency said the five defendants ranged in age from 23 to 35.
The defendants, which included a former army officer and the son of a radical preacher, appeared in court amid heavy security.
John Granville, 33, and his Sudanese driver were killed in the early hours of New Year's Day when another vehicle cut off their car and opened fire, before fleeing the scene.
Sudanese officials had insisted the assassination was not a terrorist attack, though a previously unknown group called Ansar al-Tawhid took responsibility for the killing in an Internet chat room on a militant Web site. The claim could not be verified.
It was the first time an American had been killed in Sudan since 1973, when two diplomats were assassinated by Palestinian militants.
U.S. diplomats attended the trial opening. "We are going to follow the proceedings very closely," U.S. embassy official Joel Maybury said.
Following the January shooting a team of FBI agents was sent to Khartoum to work with Sudanese authorities on the investigation.
The session was adjourned until Aug. 31.