Chauvin trial: police testify against former colleague in dramatic second week

The trial of Derek Chauvin, the white former police officer charged with murdering George Floyd in Minneapolis last May, completed its 10th day of witness testimony on Friday.

Related: Chauvin trial: vivid testimony and focus on deadly force in dramatic first week

The second week was very different from the first but no less dramatic. The opening days of prosecution witness testimony last week focused on viral, harrowing bystander video and newly released footage of Floyd’s agonizing death, then on the accounts of some traumatized bystanders.

In the second week, two key witnesses formed striking bookends. The Minneapolis police chief, Medaria Arradondo, testified against Chauvin on Monday. On Friday Andrew Baker, who performed the autopsy, took the stand. He classified the death as a homicide, which he said in a medical context meant that it resulted from the actions of a person or persons but did not imply any criminal action.

Floyd, a 46-year-old Black man, died after Chauvin, 45, kneeled on his neck for more than nine minutes.

The killing galvanised the Black Lives Matter movement and triggered the biggest civil rights protests since the 1960s in a reckoning on police brutality and entrenched racism.

Chauvin denies all charges.

Key points from the second week

Police chief says Chauvin violated department policy, training and ethics

Arradondo, the first Black police chief in Minneapolis , told the jury he “vehemently disagreed” that there had been any justification for Chauvin to restrain Floyd the way he had.

Chauvin (who was fired the day after Floyd’s death) breached regulations, in “no way, shape or form” followed training and showed a disregard for police principles to respect “the sanctity of life”, the chief said.

Cracks in the ‘blue wall of silence’

Arradondo was the biggest name in a succession of serving officers who testified against Chauvin, their former colleague of 19 years.

The civil rights lawyer David Henderson told MSNBC he had never seen multiple police officers cross the “blue line” and testify against one of their own, as the Minnesota Spokesman-Recorder related it.

He added: “I think George Floyd is going to continue to transform the world … There’s going to be a clear line drawn between how these cases are tried prior to George Floyd’s death … and after.”

But “at the same time”, he said, “police problems are systemic”.

The CNN commentator Van Jones described Arradondo’s transparent approach as “what we want from modern policing … This is the professionalism people have been begging for for 20 to 30 years.”

Experts cite George Floyd’s inability to breathe under Chauvin’s pressure

Martin Tobin, a pulmonary and critical care specialist for 40 years, told the jury on Thursday Floyd had been caught in a “vice” between Chauvin and the street.

“Mr Floyd died from a low level of oxygen and this caused damage to his brain,” he said, adding that in turn caused Floyd’s heart to stop. Tobin said: “A healthy person subjected to what Mr Floyd was subjected to would have died.”

A challenging Friday for the prosecution

The forensic pathologist Lindsey Thomas testified: “The activities of the law enforcement officers resulted in Mr Floyd’s death.”

The defense lawyer Eric Nelson wants to show that Floyd died of heart problems combined with drug use. Thomas agreed that Floyd’s underlying heart condition “was a potential cause of death”.

The week concluded with testimony from Baker, the Hennepin county chief medical examiner whom Thomas helped to train. He stopped short of backing expert witnesses who testified that Floyd was asphyxiated by Chauvin’s knee.

Baker told the court the officer pinning the man to the ground was “just more than Mr Floyd could take” by making it hard for him to breathe, causing stress hormones that worsened a heart condition and led to his death.

It was a subtle point, but the defense will look to exploit any sense of doubt.

The trial continues.