(CNN) -- The second day of Derek Chauvin's trial in George Floyd's death is set to begin Tuesday with further questioning of a professional mixed martial arts fighter who stumbled onto the scene of the 46-year-old Black man's final moments.
Donald Wynn Williams II began testifying Monday as the third witness in the trial. Relying on his own MMA experience, he said that Chauvin performed a "blood choke" on Floyd and adjusted his positioning several times to maintain pressure on Floyd's neck.
He testified he watched Floyd gasp for air, his eyes roll to the back of his head and blood start to come out of his nose.
His testimony was abruptly cut off Monday because of a technological issue.
The opening statements in Chauvin's trial came 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.
In opening statements, prosecuting attorney Jerry Blackwell said Chauvin used excessive and unreasonable force when he knelt on Floyd for 9 minutes and 29 seconds -- a number different than the infamous 8:46 timing that has become a symbol of police brutality. Chauvin's defense accepted the new timing as accurate.
Blackwell also played the harrowing video and audio of Floyd's death recorded by a bystander to bolster his argument. In response, defense attorney Eric Nelson argued that Chauvin was following his police training and said Floyd's cause of death was a combination of drug use and preexisting health issues.
"The use of force is not attractive, but it is a necessary component of policing," he said.
The first day of witness testimony also featured a Minneapolis 911 dispatcher. She was able to watch live video of Floyd's arrest at the time and called a police sergeant afterward to voice her concerns about the arrest.
"My instincts were telling me that something's wrong. Something was not right. I don't know what, but something wasn't right," Jena Scurry said she thought as she watched the video. "It was an extended period of time."
An employee at a Speedway gas station across the street also testified as prosecutors showed videos she filmed of Floyd's arrest.
The trial is being broadcast live in its entirety, giving the public a rare peek into the most important case of the Black Lives Matter era. Witness testimony in the trial is expected to last about four weeks, followed by jury deliberations.
The second-degree murder charge says Chauvin intentionally assaulted Floyd with his knee, which unintentionally caused Floyd's death. The third-degree murder charge 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.
Chauvin could be convicted of all, some, or none of the charges. Minnesota's sentencing guidelines recommend about 12.5 years in prison for each murder charge and about four years for the manslaughter charge.
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