﻿Nearly 15 months after a white nationalist rally erupted into violence in Charlottesville, Virginia, a jury heard conflicting accounts of what caused a man to drive his car into a group of counter-protesters, killing one and injuring several others.

Opening statements were delivered on Thursday in the trial of James Alex Fields, a 21-year-old male from Ohio charged with first-degree murder for the killing of Heather Heyer, a 31-year-old paralegal and civil rights activist who was among the counter-protesters.

The 10 state charges against Fields also include malicious wounding. Fields has separately been charged with 30 federal counts of hate crimes, which could carry the death penalty. He has pleaded not guilty. The court heard from witnesses who were injured when Fields’s sedan smashed into them.

The incident in August 2017 drew national attention after Donald Trump infamously blamed both sides for the violence.

The prosecution and defense agreed on Thursday it was not in dispute that Fields was the driver of the vehicle that struck a crowd in downtown Charlottesville protesting against the “Unite the Right” rally. The crux of the case, they said, was why.

“This case isn’t about what he did. It’s about what his intent was,” said Nina-Alice Antony, one of two prosecutors representing the Commonwealth of Virginia.

Antony said prosecutors would summon several witnesses whose testimony would demonstrate that Fields intentionally rammed his Dodge Challenger into the crowd, rebuking the claim made by the defense that Fields acted in self-defense.

While Antony acknowledged Fields apologized upon being apprehended by police and expressed his belief that he was under attack, she said it would be for the jury to determine “whether those statements have any credibility”.

The defense team did not contest that Fields operated his vehicle in a manner that caused death and injury.

“This is not a whodunnit case,” said John Hill, one of Fields’s attorneys.“You’re here because you need to decide, and we need to show you, was it an intended act? Was it a malicious act?”

Recounting the tensions that swiftly escalated at the rally, Hill characterized Fields as remorseful for the loss of life and injury caused by the incident. The defense would seek to corroborate Fields’s account that he was concerned for his safety.

“The atmosphere on that day is impossible for us to recreate,” Hill said.

Throughout the opening statements, Fields looked on in silence. He wore a navy blue sweater, a checkered shirt and glasses, and sat slouched next to his attorneys.

A demonstrator holds signs featuring Heather Heyer at a rally in Chicago on 13 August 2017, the day after she was killed by James Fields. Photograph: ddp USA/Rex/Shutterstock

Seated in the front row was Heyer’s mother, Susan Bro.

Amateur video and dramatic pictures of the shocking incident were viewed around the world.

The “Unite the Right” rally in 2017 followed a Friday night demonstration when hundreds of, almost exclusively, white men carrying torches and chanting antisemitic slogans marched through town.

The following day the rally erupted in violence as far-right groups clashed with counter-protesters. Later in the day, Fields drove his car into a crowd of counter-protesters who were leaving the scene.

Fields was photographed hours before the attack carrying a shield with the emblem of a far-right hate group.

Antony said Fields sat at a distance in his car, “idling, watching them”. Then he plowed through the crowd.

Prosecutors said they would present evidence of premeditation, including two Instagram posts showing images of a car running into a crowd and a text exchange in which Fields, when told to “be careful”, allegedly responded: “We’re not the ones who need to be careful.”

James Alex Fields driving his car into a group of counter-protesters in Charlottesville, Virginia, on 12 August. Witness Marcus Martin is in the photo. Photograph: Ryan M. Kelly/AP

﻿The jury heard from two witnesses before recessing for lunch. First was Michael Webster, an eyewitness who recalled seeing the counter-protesters marching down the street chanting: “Whose streets? Our streets.”

Webster then saw a Dodge Challenger driving slowly on the street but unable to move further due to those gathered. The car reversed, Webster said, but then sped forward into the crowd and then back again – striking the counter-protesters twice.

Next to testify was Marcus Martin, who was depicted in a Pulitzer prize-winning image as he was flung in the air by the car.

Martin said he had little time to react, managing to push his then fiancee – now wife – out of harm’s way. It took more than eight months to recover from his injuries, Martin said, which included a broken ankle, twisted tibia and damaged ligaments.

Martin broke down when asked to describe Heyer, who was a friend of his wife’s. Calling her “a great person”, Martin buried his head into his hands.

“It was like a war zone downtown,” he said.

The scene outside court stood starkly in contrast to the mayhem described at the center of the day’s proceedings. A security detail guarded the courthouse, a large red brick building in the city’s historic downtown, and a barricade provided an extra layer of protection.

There were no apparent protests, although a batch of racist robocalls targeting Charlottesville residents prompted alarm in the days leading up to the trial. The calls, which originated from an Idaho-based white supremacist group called The Road to Power, made antisemitic and racist claims about Heyer’s death.

Meanwhile, a civil lawsuit accuses 25 far-right individuals and groups of conspiring to commit violence at the “Unite the Right” rally, including Richard Spencer, who is an alumnus of the University of Virginia in Charlottesville.

The criminal trial is expected to last three weeks.