Defence objects to videos of Charlie Kirk's killing

But the full videos were not aired, after defence lawyers objected out of concerns that the footage would undermine Robinson's right to a fair trial.

Legal experts say the defence team's worries are real: Media coverage in high-profile cases like Robinson's can have a direct "biasing effect" on potential jurors, said Cornell Law School Professor Valerie Hans.

"There were videos about the killing, and pictures and analysis (and) the entire saga of how this particular defendant came to turn himself in," said Hans, a leading expert on the jury system.

"When jurors come to a trial with this kind of background information from the media, it shapes how they see the evidence that is presented in the courtroom."

Defence lawyers also want to oust TV and still cameras from the courtroom, arguing that "highly biased" news outlets risk tainting the case.

Prosecutors, lawyers for news organisations, and Kirk's widow urged state District Judge Tony Graf to keep the proceedings open.

"In the absence of transparency, speculation, misinformation, and conspiracy theories are likely to proliferate, eroding public confidence in the judicial process," Erika Kirk's lawyer wrote in a court filing.

"There is no adequate substitute for open proceedings."

Prosecutors intend to seek the death penalty for Robinson, 22, who is charged with aggravated murder in the September 10 shooting of Kirk on the Utah Valley University campus in Orem. 

An estimated 3000 people attended the outdoor rally to hear Kirk, a co-founder of Turning Point USA, who helped mobilise young people to vote for President Donald Trump. 

To secure a death sentence in Utah, prosecutors must demonstrate aggravating circumstances, such as that the crime was especially heinous or atrocious. That's where the graphic videos could come into play.

Watching those videos might make people think, "'Yeah, this was especially heinous, atrocious or cruel", Hans said.