MINNEAPOLIS >> The former Minneapolis police officer charged with killing George Floyd went on trial today, with prosecutors promptly showing the jury the video of Derek Chauvin pressing his knee on the Black man’s neck for several minutes as onlookers yelled at Chauvin to get off and Floyd gasped that he couldn’t breathe.

In opening statements, prosecutor Jerry Blackwell told the jury that the number to remember was 9 minutes, 29 seconds — the amount of time Chauvin had Floyd pinned to the pavement with his knee last May in the case that triggered scattered violence and a national reckoning over racial injustice.

The white officer “didn’t let up, he didn’t get up,” even after a handcuffed Floyd said 27 times that he couldn’t breathe and went motionless, Blackwell said.

“He put his knees upon his neck and his back, grinding and crushing him, until the very breath — no, ladies and gentlemen — until the very life was squeezed out of him,” the prosecutor said.

Chauvin attorney Eric Nelson countered by arguing: “Derek Chauvin did exactly what he had been trained to do over his 19-year career.”

Floyd was resisting arrest, and Chauvin arrived to assist other officers who were struggling to get Floyd into a squad car as the crowd around them grew larger and more hostile, Nelson said.

The defense attorney also disputed that Chauvin was to blame for Floyd’s death.

Floyd had none of the telltale signs of asphyxiation and had fentanyl and methamphetamine in his system, Nelson said. He said Floyd’s drug use combined with his heart disease and high blood pressure, as well as the adrenaline flowing through his body, to cause his death from a heart rhythm disturbance.

“There is no political or social cause in this courtroom,” Nelson said. “But the evidence is far greater than 9 minutes and 29 seconds.”

The medical examiner’s autopsy noted fentanyl and methamphetamine in Floyd’s system but listed his cause of death as “cardiopulmonary arrest, complicating law enforcement subdual, restraint, and neck compression.”

Chauvin, 45, is charged with unintentional second-degree murder, third-degree murder and manslaughter.

The widely seen video sparked outrage across the U.S. and led to widespread protests and unrest, along with demands that the country confront racism and police brutality. Confederate statues and other symbols were pulled down around the U.S., and activists demanded that police department budgets be cut or overhauled.

Playing the footage during opening statements underscored the central role video will play in the case. It was posted to Facebook by a bystander who witnessed Floyd’s arrest after he was accused of trying to pass a counterfeit $20 bill at a convenience store.

“My stomach hurts. My neck hurts. Everything hurts,” Floyd says, and “I can’t breathe officer.” Onlookers repeatedly shout at the officers to get off the 46-year-old Floyd. One woman, identifying herself as a city Fire Department employee, shouts at Chauvin to check Floyd’s pulse.

Jurors watched intently as the video played on multiple screens, with one drawing a sharp breath as Floyd said he couldn’t breathe. Chauvin sat calmly during the opening statements and took notes, looking up at the video periodically.

The timeline differs from the initial complaint filed last May by prosecutors, who said Chauvin held his knee on Floyd’s neck for 8 minutes, 46 seconds. In the following weeks, demonstrators staged “die-ins” lasting 8 minutes, 46 seconds, and 8:46 became a rallying cry in the case. The time was revised during the course of the investigation.

Fourteen people in the jury box will hear the case — eight of them white, six of them Black or multiracial, according to the court. Two of the 14 will be alternates. The judge has not said which ones will be alternates and which ones will deliberate the case.

Legal experts fully expected prosecutors to play the video to the jury early on.

“If you’re a prosecutor you want to start off strong. You want to frame the argument — and nothing frames the argument in this case as much as that video,” said Jeffrey Cramer, a former federal prosecutor and managing director of Berkeley Research Group in Chicago.

Blackwell said bystander witnesses would include a Minneapolis Fire Department first responder who wanted to administer aid. He said Chauvin pointed Mace at her.

“She wanted to check on his pulse, check on Mr. Floyd’s well-being,” Blackwell said. “She did her best to intervene. When she approached Mr. Chauvin …. Mr. Chauvin reached for his Mace and pointed it in her direction. She couldn’t help.”

About a dozen people chanted and carried signs outside the courthouse as Floyd family attorney Ben Crump, the Rev. Al Sharpton and members of the Floyd family went inside. The group also carried a makeshift coffin with flowers on top.

Crump said the trial would be a test of “whether America is going to live up to the Declaration of Independence.” And he blasted the idea that it would be a tough test for jurors.

“For all those people that continue to say that this is such a difficult trial, that this is a hard trial, we refute that,” he said. “We know that if George Floyd was a white American citizen, and he suffered this painful, tortuous death with a police officer’s knee on his neck, nobody, nobody, would be saying this is a hard case.”

The trial is expected to last about four weeks at the courthouse in downtown Minneapolis, which has been fortified with concrete barriers, fences and barbed and razor wire. City and state leaders are determined to prevent a repeat of the riots that followed Floyd’s death, and National Guard troops have already been mobilized.

The key questions will be whether Chauvin caused Floyd’s death and whether his actions were reasonable.

For the unintentional second-degree murder charge, prosecutors have to prove Chauvin’s conduct was a “substantial causal factor” in Floyd’s death, and that Chauvin was committing felony assault at the time. For third-degree murder, they must prove that Chauvin’s actions caused Floyd’s death and were reckless and without regard for human life.

The manslaughter charge requires proof that Chauvin caused Floyd’s death through negligence that created an unreasonable risk.

Unintentional second-degree murder is punishable by up to 40 years in prison, and third-degree carries up to 25 years, but sentencing guidelines suggest that Chauvin would face 12 1/2 years in prison if convicted on either charge. Manslaughter is punishable by up to 10 years.