Clark is charged with first-degree murder in the New Year's Day 2007 drive-by shooting death of Williams, who was riding in a rented limousine after leaving a Denver nightclub. An indictment says Williams and Clark had been at the club with separate groups that exchanged taunts.
Williams died inside the limousine in Walker's arms. During an interview months later on HBO's "Real Sports," Walker said then-teammate Brandon Marshall and his cousin exchanged angry words with two men who confronted Williams and his group after taking offense when Marshall sprayed them with champagne. It was unclear whether Marshall would be called to testify.
Clark has said he wasn't involved in the shooting.
Dressed in bright red jail clothes, Clark leaned over to his defense attorneys and grimaced at District Judge Christina Habas as she ruled on several technical matters.
"I know you may not agree with everything I'm doing, but please, don't react," Habas sternly told Clark.
Despite restrictions on communicating with people in custody, two Clark supporters audibly kissed their hands and blew in Clark's direction as they left the courtroom. State court administrator Rob McCallum did not immediately know if those two, a young man and woman, face any sanctions.
Clark is a suspected gang member known as "Little Let Loose" and "Lil Willie." He and two others face murder charges in the shooting death of Kalonniann Clark in Denver in December 2006. She was killed the day before she was to testify in an unrelated drug case.
Chief Deputy District Attorney Timothy Twining has said that many witnesses are fearful for their lives and asked to be allowed to testify in private in Habas' chambers.
Instead, Habas imposed strict security measures, including screenings with metal detectors at the courthouse entrance and outside the courtroom. She banned any communication from inside the courtroom, which means no cell phones, texting or using the Internet, partly to keep the movements of witnesses secret.
Cameras are also banned from the entire fourth floor of the courthouse.
Habas will allow a sketch artist in the courtroom but with several restrictions, including an explicit prohibition on drawing the face of star prosecution witness Daniel Harris, who once faced federal drug charges that carried up to life in prison.
According to testimony in court, Harris is now in the witness protection program.
Twining said Harris' inability to testify against Clark would "jeopardize this case."
Habas also banned any sports team logos, jerseys, pins or jewelry, including any Super Bowl championship rings that may be worn by Broncos players or staff.
"I'm trying very hard to not make this a circus," Habas said.