A federal grand jury has indicted four former Minneapolis police officers who were involved in George Floyd’s arrest and death, accusing them of willfully violating the Black man’s constitutional rights while he was restrained face-down on the pavement and gasping for air. Derek Chauvin, Thomas Lane, J. Kueng, and Tou Thao are named in a three-count indictment unsealed Friday.

Chauvin is specifically charged with infringing on Floyd’s right to be free from unreasonable seizure and unreasonable force by a police officer. Thao and Kueng are also accused of violating Floyd’s right to be free from unreasonable seizures, claiming they did not intervene to stop Chauvin from kneeling on Floyd’s neck. All four officers have been charged with failing to provide Floyd with medical care.

Floyd’s May 25 arrest and death, which a bystander captured on cellphone video, sparked protests nationwide and widespread calls for an end to police brutality and racial inequities.

Chauvin was also charged in a second indictment, stemming from the arrest and neck restraint of a 14-year-old boy in 2017. Lane, Thao, and Kueng appeared in U.S. District Court in Minneapolis via videoconference on Friday. Chauvin did not attend the court hearing.

Chauvin was convicted last month on state murder and manslaughter charges in Floyd’s death and is being held in Minnesota’s only maximum-security prison while awaiting sentencing. The other three former officers are scheduled for a state trial in August and are free on bond. They were allowed to remain free following their appearance in federal court on Friday.

Floyd, 46, died after Chauvin pinned him to the ground with a knee on his neck, despite Floyd’s repeated claims that he couldn’t breathe while handcuffed. Kueng and Lane also assisted in Floyd’s restraint; according to state prosecutors, Kueng knelt on Floyd’s back and Lane held Floyd’s legs down. According to state prosecutors, Thao restrained bystanders and prevented them from intervening during the 9 1/2-minute restraint.

During Chauvin’s murder trial, his attorney, Eric Nelson, argued that Chauvin acted reasonably in the situation and that Floyd died as a result of underlying health issues and drug use. He has requested a new trial, citing a variety of issues, including the judge’s refusal to move the trial due to public scrutiny.

Nelson did not respond to the federal charges on Friday. Messages left with attorneys for two of the other officers were not returned immediately, and an attorney for the fourth officer was about to enter an elevator when he was disconnected.

Prosecutors must believe that an officer acted under the “color of law,” or government authority, and willfully deprived someone of their constitutional rights, including the right to be free from unreasonable seizures or the use of unreasonable force, in order to bring federal charges in police-involved deaths. That is a high legal standard; an accident, poor judgment, or simple negligence on the part of the officer is insufficient to support federal charges.

According to Roy Austin, a former deputy assistant attorney general in the Department of Justice’s Civil Rights Division who prosecuted such cases, prosecutors must prove that the officers knew what they were doing was wrong at the time but did it anyway.

Conviction on a federal civil rights charge is punishable by up to life in prison or the death penalty, but such harsh sentences are extremely rare, and federal sentencing guidelines rely on complicated formulas that indicate the officers would receive far less if convicted.

In Chauvin’s case, if the federal court charges him with second-degree murder, he could face anywhere from 14 to slightly more than 24 years in prison, according to Mark Osler, a former federal prosecutor and professor at the University of St. Thomas School of Law.

According to the first indictment, Thao and Kueng were aware Chauvin had his knee on Floyd’s neck and “willfully failed to intervene to stop Defendant Chauvin’s use of unreasonable force” even after Floyd became unresponsive.

For their alleged deliberate indifference to Floyd’s medical needs, all four officers are charged with willfully depriving Floyd of liberty without due process.

Chauvin was found guilty of unintentional second-degree murder, third-degree murder, and second-degree manslaughter. When he is sentenced in June, he will most likely face no more than 30 years in prison, according to experts. The other officers are accused of assisting and abetting second-degree murder and manslaughter. The four officers were all fired.