Cristhian Bahena Rivera, the man charged with first-degree murder in the slaying of University of Iowa student Mollie Tibbetts, has requested to delay a hearing in which a judge will determine whether police infringed upon his constitutional rights against self-incrimination.

According to the Des Moines Register,court documents filed June 18 show Rivera has asked to move the hearing to give his lawyers more time to prepare. The hearing to review his motion to suppress evidence is scheduled for June 25.

Eighth District Court Judge Joel Yates had not responded as of 11 a.m. June 18, according to the Register.

Rivera, 25, was charged in 2018 after reportedly confessing to abducting Tibbetts while she was on a run July 18 near Brooklyn, Iowa.

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Rivera’s lawyers are requesting the delay to have more time to review evidence and talk with an expert witness. According to the Register, they specifically wanted to review the results of a May search warrant of Rivera’s Google account and location information from July 18 and July 23. The results have not been disclosed.

State attorneys didn’t oppose the request; however, they did ask Rivera to waive his rights to a speedy trial, because he had already said he would, according to online court records. Rivera has until Sept. 18 to waive his rights.

Rivera’s attorneys filed the motion to suppress evidence because they argue he was not read his Miranda rights until nine or 10 hours into his interview with law enforcement, which lasted 12 hours, according to the Register. Therefore, any confession he made during that time was involuntary. They also said he was not told of his right to an attorney or his right to decline to cooperate.

According to the Register, the attorneys identified factors of the case they found concerned in the June 18 motion, including the language barrier and Rivera’s lack of education. They also said he was offered leniency, which can “induce false confessions leading to wrongful convictions of the innocent.”

According to court documents released May 31, the Cedar Rapids Gazette reported, Rivera was read his Miranda rights in Spanish at approximately 11:30 p.m. during interviews that went from the evening of Aug. 20 to the morning of Aug. 21.

“During the interview, both before and after Miranda warnings were read, the defendant made several admissions concerning his involvement in the disappearance and death of Mollie Tibbetts. Following the interview, the defendant led law enforcement to the location of Mollie Tibbetts’s body,” the documents stated.

The trial remains set for Sept. 3 in Woodbury County. Rivera faces life in prison without parole if convicted.