Experts say Derek Chauvin could face jail of up to 40 years if convicted. Photo / Supplied
The former Minneapolis police officer who used his knee to apply pressure to the neck of handcuffed black man George Floyd did so for almost three minutes after Floyd lost consciousness.
For the full eight minutes and 46 seconds that officer Derek Chauvin held his knee to Floyd's neck, cameras were rolling. Floyd was begging for air and did not appear to be resisting.
Chauvin has been fired from his job and charged with second-degree murder — a charge most casual observers would agree has a good chance of leading to a conviction.
Experts say Chauvin could face jail of up to 40 years if convicted but it's a big "if". It's a reason so few police officers are ever convicted of murder in the United States.
For a homicide conviction to be upheld under Minnesota law, prosecutors must prove beyond a reasonable doubt that Chauvin intended to kill Floyd. And that could be difficult.
As The Dispatch reported, a single contrarian juror is the difference between 25 years in prison and freedom.
Dr Jennifer Cobbina, assistant professor and criminologist at Michigan State University, told The Independent that members of the force were almost immune to conviction.
"When officers are charged, regardless of that the charge is, they generally are not convicted," she said.
"If they are convicted, it's usually when the incident is incredibly egregious, which obviously is the case with George Floyd.
"If they are convicted, they're rarely sentenced to a term of imprisonment or certainly not a long term of imprisonment."
Professor Kami Chavis, from Wake Forest University's School of Law, told the ABC on Thursday the case against Chauvin included "some very damning video evidence" but "these can be very difficult cases to try".
The director of the school's criminal justice programme said America's justice system historically sided with law enforcement.
"In our country we've really had, we've really had difficulties securing prosecutions in these cases and even when you get a grand jury to indict or have charges filed, if they go to trial, it doesn't mean they're always successful," she said.
"These can be very difficult cases to try. Some of that just has to do with the fact that police officers often get the benefit of the doubt. What's different here is we do have some very damning video evidence."
Minnesota Attorney-General Keith Ellison announced on Wednesday a third-degree murder charge against Chauvin had been upgraded to a second-degree murder charge.
The key distinction between the two, according to Minnesota Legislature, is that murder in the third degree is described as being "without intent to effect the death of any person", while murder in the second degree involves intent.
Importantly, prosecutors do not have to prove premeditation.
"Trying this case will not be an easy thing. Winning a conviction will be hard," he said.
"I say this not because we doubt our resources or our ability. In fact we're confident in what we're doing. But history does show that there are clear challenges here.
"It is better to make sure that we have a solid case, fully investigated, before we go to trial, than to rush it."
The three other officers present at Floyd's arrest last week have been charged with aiding and abetting second-degree murder.
J Alexander Kueng and Thomas Lane helped hold Floyd down before he died. Tou Thao stood nearby and kept bystanders from intervening.