Nichols' attorneys had said deliberations were contaminated because two jurors admitted conversing about the case privately, which violated the judge's instructions.
But U.S. District Judge Richard Matsch rejected that argument Tuesday, noting the jurors were confined to an exclusive space in the courthouse during their work. "There is nothing to indicate that any jurors discussed this case outside of the courthouse," he wrote.
Nichols, 43, was convicted of involuntary manslaughter and conspiracy but was acquitted of murder and weapons charges in the April 19, 1995, bombing of the Alfred P. Murrah Federal Building. The blast killed 168 people and injured hundreds.
Nichols was sentenced to life in prison, and he has filed a notice of intent to appeal. Timothy McVeigh, his former Army buddy, has appealed his death sentence and conviction on murder, conspiracy, and weapons-related counts.
During his sentencing June 4, Nichols' attorneys filed the motion for a new trial, contending jurors had violated Matsch's instructions that they deliberate only as a group. The motion was based on a May 31 Rocky Mountain News interview with jurors.
In the article, jurors Todd Fockler and Tim Burge, who favored conviction, said they were stunned when the panel voted 10-2 for acquittal in an initial straw poll.
The newspaper said the two men discussed the case privately, and quoted Fockler as saying, "I am not acquitting him until we've seen every piece of evidence."
Prosecutors argued that jurors may have talked outside the group, but their conversations were not enough to warrant a new trial.