Four former Minneapolis police officers charged in the May 25 killing of George Floyd face unprecedented issues as their cases proceed toward trial: Their actions were captured on a lengthy video; they each have a stake in the outcomes, and several bystanders witnessed the death.

Derek Chauvin, who knelt on Floyd's neck for nearly eight minutes, and his three former colleagues — J Alexander Kueng, Thomas Lane and Tou Thao, who assisted in his arrest — are scheduled to make their second court appearance Monday afternoon on charges ranging from second-degree murder to aiding and abetting murder.

Veteran defense attorneys say the prosecution's case against Chauvin is strong, while a series of unique circumstances pose challenges to both prosecutors and defense attorneys at the center of a case that has captured worldwide attention.

"There are cases you can never win; this very well may be one of them," said defense attorney Joe Friedberg, who has handled about 100 murder cases.

Chauvin is charged with one count each of second-degree unintentional murder, third-degree murder and second-degree manslaughter. His attorney, Eric Nelson, declined to comment on the case. The other three are charged with aiding and abetting murder and manslaughter.

The Floyd case differs in key ways from the last three times an officer was tried in Minnesota for killing a civilian. Floyd's killing lasted nearly eight minutes instead of the "split-second" decisions that previous officers faced, providing their attorneys an argument that they were justified in using deadly force.

By contrast, Floyd warned the officers of his own impending death after repeatedly telling them he couldn't breathe. Bystanders also repeatedly warned the officers and begged them to relent.

The fact that all three officers who assisted Chauvin in arresting Floyd were also charged could cause a crack in the "blue wall of silence" that has seemingly protected some officers previously accused of crimes.

"Ultimately the duty of every witness is to tell the truth, but the reality is human beings remember things differently, and the reality is all human beings have biases," said Ramsey County Attorney John Choi, whose office tried two of the last three officers charged with killing civilians. "I think there's enormous pressure on the police witness to be helpful to the partner accused of a crime, and that's a product of the police culture that we have."

When Washington County Deputy Brian Krook was tried three months ago in the fatal shooting of a suicidal man, prosecutors told jurors his colleague, Deputy Joshua Ramirez, was the epitome of good police work.

Ramirez peacefully negotiated for about 35 minutes with Benjamin Evans, who had a gun but did not threaten first responders before Krook shot at Evans without warning.

But when Ramirez testified, he said that perhaps he had negotiated with Evans for too long, implying that he should have taken deadly action himself.

"How long were you willing to wait for [Evans] to put the gun down?" asked prosecutor Thomas Hatch, an assistant Ramsey County attorney who tried the case so Washington County could avoid a conflict of interest.

"I don't know," Ramirez said. "Maybe I waited too long."

Hatch pressed Ramirez, asking whether Evans' actions caused him to consider shooting him.

"Yes," Ramirez replied. He acknowledged that he had previously said no to the same question before the grand jury that indicted Krook on second-degree manslaughter charges.

Krook was acquitted in mid-March.

During former Minneapolis officer Mohamed Noor's trial last year in the 2017 fatal shooting of Justine Ruszczyk Damond, Hennepin County prosecutors openly challenged the credibility of several Minneapolis police officers, as well as investigators from the Minnesota Bureau of Criminal Apprehension, implying that they colluded to obscure or create evidence.

Noor was convicted and is appealing the case.

With all three of his former colleagues facing potential prison time, Chauvin likely won't have the same support network, said some prominent lawyers.

"One of the factors of any witness is that they will testify in a manner that is consistent with their self-interest," said lawyer Don Lewis, who helped Choi's office charge former officer Jeronimo Yanez in the 2016 killing of Philando Castile. "Officer Chauvin isn't going to have much support from his colleagues available."

At their first appearances earlier this month, attorneys for Lane and Kueng — Earl Gray and Thomas Plunkett, respectively — blamed Chauvin for Floyd's death. The attorneys argued that their clients were rookies who relied on Chauvin, a 19-year veteran and training officer, for guidance at the scene.

Gray said he'll soon file a motion to dismiss the charges against Lane, noting that Lane twice asked Chauvin if they should roll Floyd onto his side to help him breathe; he was rebuffed.

"I don't anticipate trying Mr. Lane's case with Mr. Chauvin," Gray said.

Friedberg was skeptical a judge would dismiss the charges against Lane but said Gray had a strong defense should the case go to trial.

"The things the young man [Lane] said out loud, the relationship between Chauvin and the young man, and it's clear that young man had no intent for Floyd to die because he did CPR" on Floyd, Friedberg said. "That's going to be a huge issue."

However, some said, a savvy Chauvin defense could turn the tables.

He could direct the blame at Lane, who was holding down Floyd's leg as Floyd lay stomach-down in the street, and Kueng, who was holding onto Floyd's back, said lawyer Robert Richman.

"It seems that keeping someone … in a prone position on your stomach and having pressure placed on your back causes respiratory difficulties," Richman said, postulating that perhaps "it was the other two officers holding him down that caused the breathing difficulties," rather than Chauvin kneeling on the side of Floyd's neck.

Prosecutors also could face challenges trying to prove the four former officers shared the same intent, along with trying to navigate complications raised by two slightly competing autopsy reports.

The Hennepin County Medical Examiner's Office found that Floyd died when his heart stopped while he was being restrained, noting that the presence of fentanyl intoxication and recent methamphetamine use were "other significant conditions."

Attorneys for Floyd's family criticized that report and commissioned an independent autopsy that concluded Floyd died of asphyxia.

Friedberg found an argument for the defense in those autopsies.

"I would take the position that [Floyd] had started to die before Chauvin put his knee on his neck," he said.

"He had taken some deadly drugs," Friedberg noted, citing the fentanyl that killed Prince and many others in recent years. "Make your argument a scientific argument instead of an emotional argument or state-of-mind argument."

Chao Xiong • 612-270-4708

Twitter: @ChaoStrib