Defense lawyers for the man charged with killing University of Iowa student Mollie Tibbetts are asking for his upcoming trial to be delayed.

Lawyers for Cristhian Bahena Rivera say they need a delay in the Feb. 4 trial date so that they have time to appeal a judge's ruling that allowed key evidence to be used against their client.

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The Iowa Supreme Court will consider whether to take the appeal before trial. Rivera's lawyers also say they would now like to depose several individuals recently added to the prosecution's witness list, including Tibbetts' boyfriend at the time of her July 2018 disappearance.

The defense claims fingerprint and blood evidence found in Rivera’s trunk has not been compared to any other individual’s fingerprints. The defense argues that the fingerprints do not belong to Rivera, and that the blood is a mixture belonging to Tibbetts and another unidentified person.

Prosecutors say the defense has had the reports relating to each of the witnesses for some time and that the defense had no prior objections to the fingerprint evidence.