Judge says comments to the media by prosecutors about defendant violate rules of what can be said outside of court.

The Utah judge presiding over the Charlie Kirk murder case has held prosecutors in contempt of court over comments they made to media organisations about defendant Tyler Robinson.

On Friday, Judge Tony Graf said the comments violated his restrictions on what the two sides can say about the case outside of court.

But Graf denied a defence request to take the death penalty off the table as a sanction for the violation.

He said the problem could instead be resolved through the screening and questioning process for potential jurors, which is intended to weed out people who could be biased about the case.

Robinson, a 23-year-old from southwestern Utah, has not yet entered a plea.

He is charged with aggravated murder in the September 10 assassination of Kirk, an ally of United States President Donald Trump who was shot in the neck while addressing a crowd of thousands at Utah Valley University.

Defence lawyers accused Deputy Utah County Attorney Christopher Ballard of trying to influence potential jurors by going on a “media tour” to talk about ballistics evidence in the case. Ballard also said prosecutors had enough evidence to show Robinson murdered Kirk.

Legal experts had said blocking the death penalty would have been an extreme remedy. Graf said it would have been “grossly disproportionate” to the misconduct.

Ballard argued that he had a right to speak to the news media to correct misinformation about a preliminary finding by ballistics experts.

Those experts’ initial tests did not match the bullet fragment with a gun that investigators believe was used to kill Kirk. That spurred stories by some publications raising questions about the prosecution’s case.

A March 30 headline in the United Kingdom-based Daily Mail, for example, reported that the bullet that killed Kirk “did NOT match” the rifle that investigators say was used.

Ballard said he was trying to “set the record straight” when he told media organisations the ballistics tests were inconclusive to determine whether the bullet was fired from the suspected murder weapon.

Conjecture over that evidence fuelled unsubstantiated conspiracy theories that there might have been a second shooter, or that Kirk’s death was staged. Lawyers on both sides have raised concerns that the misinformation and extensive media attention could taint the potential jury pool.

Graf said the comments about the bullet did not violate the court’s rules, but that Ballard went too far when he went on to say that prosecutors had “ample evidence to demonstrate beyond a reasonable doubt that Tyler Robinson committed this murder”.

The judge said those additional public statements possessed a “substantial likelihood” of prejudicing the case.

The judge added that the comments were not made out of any malicious desire by prosecutors to taint the jury pool, and that his ruling had nothing to do with the charges against Robinson.

“Its sole purpose is enforcement of a narrowly tailored publicity order governing attorney conduct,” Graf said.

Authorities have said DNA consistent with Robinson’s was found on the trigger of the rifle, the fired cartridge casing, two unfired cartridges and a towel used to wrap the rifle.

The Associated Press news agency left telephone and email messages seeking comment from prosecutors and Robinson’s lawyers.