Every victim "shall have the right to be present at all critical stages of these proceedings," wrote Arapahoe County District Judge Carlos A. Samour Jr. in a 30-page order issued Wednesday.
Holmes faces 166 charges in the shooting of 82 theatergoers who were among more than 400 attending a showing of a Batman movie in Aurora, Colorado. Twelve people died and 70 were wounded in the midnight rampage.
Holmes' lawyers in the capital case had called for witnesses to be excluded from pretrial hearings and from the trial to ensure their testimony would not be influenced by others' testimony.
But Samour noted that Colorado's Constitution provides crime victims the right to be present "at all critical stages of the criminal justice process" unless their presence would interfere with the defendant's right to a fair trial.
"The record does not support the conclusion that excluding the victims from the critical stages of the proceedings is necessary to protect the defendant's constitutional right to a fair trial," he wrote.
He said the defense had not even alleged that Holmes' right to a fair trial would be affected by the victims' courtroom presence during the trial.
Samour defined "victims" as any of the approximately 750 people who were inside the theater during the shootings or in an adjacent theater, where some of the bullets landed.
Samour took the defense to task, asserting that its submissions "fall woefully short."
He said the victims likely to testify at trial had already provided recorded statements and would be "subject to impeachment" if they were to change their testimony.
And he noted that Holmes had not sought to sequester victims from a 2-1/2-day preliminary hearing during which the prosecution detailed its case.
The case, he said, is likely to center on whether the 25-year-old defendant -- who has pleaded not guilty by reason of insanity -- was sane at the time of the shootings. And that, he said, is a matter more likely to be addressed by mental health experts than by the theatergoers.