Watch live coverage of the trial on HLN starting at 10 a.m. ET daily.

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Former Minneapolis Police officer Derek Chauvin knelt on George Floyd’s head and neck for 4 minutes and 45 seconds as Floyd cried out for help, stayed on his neck as Floyd flailed and had seizures for 53 seconds, and then remained on a non-responsive Floyd for another 3 minutes and 51 seconds, prosecutors said during opening statements in Chauvin’s criminal trial on Monday.

“Mr. Derek Chauvin betrayed this badge when he used excessive and unreasonable force upon the body of Mr. George Floyd,” prosecuting attorney Jerry Blackwell said. “That 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 opening statements from Blackwell, as well as a rebuttal from Chauvin’s defense team, highlighted the first day of Chauvin’s long-awaited criminal trial. The legal wrangling comes 10 months after Floyd’s death launched a summer of protest, unrest and a societal reckoning with America’s past and present of anti-Black racism and aggressive policing.

Chauvin, 45, has pleaded not guilty to second-degree unintentional murder, third-degree murder and second-degree manslaughter charges.

Three witnesses, including a 911 dispatcher and two bystanders, also took the stand for the prosecution on Monday to lay the groundwork for Floyd’s final moments. The witness testimony phase of the trial is expected to be take about a month.

The bystander video of Floyd’s final moments, which shocked the nation last year, was also played for jurors in its entirety. Blackwell emphasized that Chauvin was on Floyd’s neck for 9 minutes and 29 seconds – an update on the initially reported 8 minutes and 46 seconds.

“This case is not about split-second decision-making,” Blackwell said.

In response, attorney Eric Nelson focused the defense’s opening statement on Floyd’s use of fentanyl and methamphetamine and his resistance to the arresting officers.

Nelson also sought to establish doubt as to the precise cause of Floyd’s death, saying it was not Chauvin’s knee, but a combination of drug use and preexisting health problems. And he defended Chauvin’s actions as being within proper training.

“You will learn that Derek Chauvin did exactly what he had been trained to do over the course of his 19-year career,” Nelson said. “The use of force is not attractive, but it is a necessary component of policing.”

In a first for Minnesota, the trial will be broadcast live in its entirety, giving the public a rare peek into the most important case of the Black Lives Matter era.

In this image from video, defense attorney Eric Nelson, left, and former Minneapolis police officer Derek Chauvin listen prior to opening statements on Monday, March 29, 2021.

On Monday morning, Floyd’s family members and several attorneys knelt for 8 minutes and 46 seconds outside the courthouse to commemorate the time Chauvin was originally reported to have stayed on Floyd’s head and neck.

“Today starts a landmark trial that will be a referendum on how far America has come in its quest for equality and justice for all,” said Floyd civil attorney Benjamin Crump.

The trial is being held at a heavily fortified Hennepin County courthouse in downtown Minneapolis, surrounded by fencing and law enforcement. Due to Covid-19 precautions, plexiglass barriers have been set up inside the courtroom and witnesses and attorneys are required to wear masks when not speaking.

MMA fighter and bystander explains a ‘blood choke’

Minneapolis 911 dispatcher Jena Scurry was the first witness in the closely watched case.

After opening statements, three witnesses testified for the prosecution about Floyd’s arrest.

The first witness in the case was Jena Scurry, a Minneapolis 911 dispatcher who directed officers to the Cup Foods store, the scene of Floyd’s death.

Scurry walked the jury through video, not previously publicly released, shot from a police camera across the street from Cup Foods. She was able to watch live video from that feed on the day of Floyd’s death and called a police sergeant to voice her concerns about the arrest.

“You can call me a snitch if you want to,” she said in the recorded call. “I don’t know if they had to use force or not. They got something out of the back of the squad and all of them sat on this man, so I don’t know if they needed to or not.”

On the stand Monday, she explained that she called because she was alarmed by what she saw during Floyd’s arrest.

“My instincts were telling me that something’s wrong. Something was not right. I don’t know what, but something wasn’t right,” Scurry said she thought as she watched the video. “It was an extended period of time.”

On cross-examination, Scurry noted that at one point Squad 330, either Chauvin or former officer Tou Thau, called for a faster ambulance response. She also acknowledged that the video showed the squad car shaking back and forth as officers and Floyd struggled during the arrest.

The second prosecution witness was Alisha Mariee Oyler, an employee at the Speedway gas station across the street from where Floyd died. She noticed that police were “messing with someone” and recorded seven cell phone videos of Floyd’s arrest from a distance, which were played in court.

“I always see the police, they are always messing with people, and it’s wrong, and it’s not right,” she told the court.

The third witness of the day was Donald Wynn Williams II, a professional mixed martial arts fighter who stumbled upon the scene of Floyd’s arrest and was one of the most vocal bystanders.

Relying on his MMA experience, he testified that Chauvin was doing a “blood choke” on Floyd, a hold on the neck that can cut off circulation to the brain. He testified that he and Chauvin made eye contact after Williams mentioned the blood choke out loud.

“When I said it, he acknowledged it,” Williams said.

His testimony will continue on Tuesday.

How two lives collided

George Floyd lost consciousness and died under the knee of former Minneapolis Police officer Derek Chauvin on May 25, 2020.

Derek Chauvin, 45, had been an officer with the Minneapolis Police Department since 2001 until he was fired in the wake of Floyd’s death.

Their lives collided on May 25, 2020, when police were called about a man who had used a $20 counterfeit bill at a Minneapolis store. Two officers were directed to a parked car with Floyd in the driver’s seat, and they handcuffed him and moved to put him into the back of a police car, according to the amended complaint.

Chauvin and another officer then arrived to the scene and struggled to get Floyd into the vehicle, the complaint states. Chauvin allegedly pulled Floyd to the ground in a prone position and placed his knee on Floyd’s neck and head. His knee remained there even as Floyd pleaded, “I can’t breathe,” said “I’m about to die” and ultimately stopped breathing, the complaint says. He was pronounced dead at a hospital shortly after.

In his opening statement, Nelson indicated that officers perceived the vocal group of bystanders watching Floyd’s death as a threat to their safety.

“They are screaming at (the officers), causing the officers to divert their attention from the care of Mr. Floyd to the threat that was growing in front of them,” said Nelson.

The Hennepin County Medical Examiner’s autopsy listed Floyd’s cause of death as heart failure due to “law enforcement subdual, restraint, and neck compression,” and ruled it a homicide. The medical examiner, Dr. Andrew Baker, also noted Floyd’s arteriosclerotic and hypertensive heart disease, fentanyl intoxication and recent methamphetamine use as “other significant conditions.”

In this image taken from video, defense attorney Eric Nelson, left, former Minneapolis police officer Derek Chauvin, right, and Nelson's assistant Amy Voss, back, introduce themselves to jurors on Monday, March 22, 2021, at the Hennepin County Courthouse in Minneapolis.

Chauvin’s defense attorneys have argued those other conditions were the real cause of death.

“The evidence will show that Mr. Floyd died of a cardiac arrhythmia that occurred as a result of hypertension, his coronary disease, the ingestion of methamphetamine and fentanyl and the adrenaline flowing through his body, all of which acted to further compromise an already compromised heart,” said Nelson.

The second-degree murder charge says Chauvin intentionally assaulted Floyd with his knee, which unintentionally caused Floyd’s death. The third-degree murder charge – which was added to the case in recent weeks – says Chauvin acted with a “depraved mind, without regard for human life.” And the second-degree manslaughter charge says Chauvin’s “culpable negligence” caused Floyd’s death.

The three charges against Chauvin are to be considered separately, so he could be convicted of all, some, or none of them.

If convicted, Minnesota’s sentencing guidelines recommend about 12.5 years in prison for each murder charge and about four years for the manslaughter charge.