Defense attorneys for Tyler Robinson, the Utah man accused of shooting Charlie Kirk, is asking for a key evidence hearing to be delayed, saying that they need more time to sift through mountains of evidence.

The lawyers also raised questions about the validity of some of the evidence against their client, including whether the bullet that struck Kirk came from the rifle police believe Robinson fired.

According to a motion filed Monday, the defense said they have been provided with a summary report from the Bureau of Alcohol, Tobacco, Firearms and Explosives which indicated that the agency was “unable to identify the bullet recovered at autopsy to the rifle allegedly tied to Mr. Robinson.”

The defense team also argued they may want to offer testimony of the ATF firearm analyst at a preliminary hearing, which is currently scheduled for mid-May. But in order to decide that, they argue, they need their experts to review the ATF case file — which has not yet been provided to them.

The motion says that state prosecutors have also indicated more bullet analyses are underway but are not yet finished.

Robinson’s attorneys similarly questioned DNA evidence in the case, arguing that reports from the FBI and ATF show both agencies gathered “minute quantities of DNA on various items of evidence,” which consist of “mixtures of up to ‘five or more’ individuals.”

The defense argued that they need time to consult with experts on that evidence and the methods government agencies used to sort out various DNA found on the samples.

FBI director Kash Patel has said that Robinson’s DNA was found on a towel wrapped around the rifle that law enforcement believed was used in the shooting, as well as a screwdriver found on the rooftop where Robinson allegedly fired a single fatal shot.

Robinson’s team has asked for at least a six-month delay. At a preliminary hearing, prosecutors present evidence in an effort to show that there is “probable cause” for the case to move forward. This is a lower evidentiary standard than at a trial, where prosecutors must prove their case “beyond a reasonable doubt.” Fourth District Court Judge Tony Graf will decide whether to bind over the case, and continue to move it toward trial.

The preliminary hearing will be the first time that evidence in the case will be presented in court. Robinson’s Monday court filing indicates that prosecutors intend to present forensic evidence and information from Robinson’s parents and roommate, along with evidence from Robinson’s phone and social media accounts.

Robinson is facing multiple charges, including aggravated murder, in connection with Kirk’s Sept. 10 death. Prosecutors have indicated they will seek the death penalty if Robinson is convicted.

He is next expected in court on April 17, where attorneys are expected to argue a motion on whether cameras will be allowed in the courtroom.