A white supremacist who triggered racial tensions throughout the nation when he rammed his car into counter-protesters of a “Unite the Right” rally in Virginia will ask a federal judge for mercy Friday at a sentencing for his hate crimes.

Lawyers for James Alex Fields Jr., 22, a self-avowed neo-Nazi who occasionally adorned his text messages with photos of Adolf Hitler, said in recent court filings that "no individual is wholly defined by their worst moments" and that Fields should not be sentenced to life in prison.

“No amount of punishment imposed on James can repair the damage he caused to dozens of innocent people. But this Court should find that retribution has limits,” Fields' lawyers wrote. "The essential property of mercy is that it applies to the undeserving."

But prosecutors will say at Friday's 9 a.m. hearing in U.S. District Court for the Western District of Virginia in Charlottesville that he deserves life in prison. He was convicted of murder in state court in December; those charges are separate from the federal hate crime charges he is being sentenced for on Friday.

"Life imprisonment is the only appropriate sentence for the defendant," federal prosecutors said in a sentencing memorandum.

Fields plowed his car into the crowd of peaceful counter-protesters on Aug. 12, 2017, killing Heather Heyer, a 32-year-old paralegal and activist, and injuring dozens of others.

Heyer's mother, Susan Bro, told USA TODAY that she is glad a conclusion is coming.

She hopes that the judge will give Fields multiple life sentences. But she's been trying not to dwell on it, hoping instead to focus on other projects, such as the Heather Heyer Foundation. The non-profit provides scholarships for young people interested in social change.

"I've tried to just leave him in the hands of justice," she said. "I have been trying to move forward with making her death count for something."

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When he was convicted in state court in December, a jury in Charlottesville recommended that Fields serve a life sentence plus another 419 years in prison. His sentencing in state court is scheduled for July.

At Friday's federal sentencing, Fields, of Maumee, Ohio, will face the outcome of the guilty plea he made at the end of March to 29 hate crimes. As a part of that deal, one charge was dropped: The death penalty was taken off the table.

"This is a unique case. The government has been unable to identify any prior cases involving similar motivation, conduct, and consequences," prosecutors wrote.

They argued that typically, a federal first-degree murder charge carries a life sentence.

Heyer was killed the last day of an August weekend rally organized by white supremacists and their sympathizers protesting the removal of Robert E. Lee's statue from a Charlottesville park. The highly publicized event drew supporters and counter-protesters to the university town in central Virginia.

According to the indictment, Fields traveled to Charlottesville to participate in the rally that was widely publicized on social media as associated with white supremacist individuals and other far-right groups.

After authorities declared the event an "unlawful assembly," Fields left the area, but returned in his car as crowds drifted away from the site of the rally, the indictment charged. He then encountered a group of counter-protesters who were chanting and carrying signs promoting equality and protesting against racial discrimination.

The indictment alleged that Fields slowly backed up his car in a downtown street then rapidly accelerated, ran through a stop sign and across a raised pedestrian mall, and drove directly into the crowd, hitting numerous people, killing Heyer, and injuring many others. He then fled the scene.

Court papers say Fields showed remorse when he apologized to police officers after the fatal wreck and wept when he learned that someone died.

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The defense's argument for a lesser sentence is couched in Fields' struggles. In a defense memo, Fields' lawyers argued that the court should consider his history of mental illness and childhood trauma. Mental health experts who testified in court proceedings said Fields had been diagnosed with bipolar disorder and schizoid personality disorder at the ages of 6 and 14.

Bro said that she understands that there is conflict in determining Fields' sentence.

"I understand the young man has mental health issues," she said. "I've known a lot of people that have those same issues, but did not choose to kill someone."

Fields was 20 years old at the time of the attack. The defense said that a life sentence without parole would be "unconstitutionally cruel and unusual" for someone that young.

Bro said she is worried that anything but a life sentence will send the wrong message, particularly for copycats.

Regardless of the result, Bro said she hopes that Fields gets help in prison and that he can one day help others leave the hate movement.

"You never know what a judge is going to say or do," said Bro. "And I'm a little anxious about it. But I really have no control over it."

Follow Morgan Hines on Twitter: @MorganEmHines.