A "Black Lives Matter" sign stands on my lawn. Former Minneapolis police officer Derek Chauvin wouldn't want me on his jury. But Chauvin's trial should be fair, and Hennepin County District Judge Peter Cahill's decision to allow prosecutors to present "spark of life" evidence makes a fair trial unlikely.

Minnesota appears to be the only state that allows a prosecutor to present sympathetic depictions of a victim's entire life while a homicide defendant is on trial.

Minnesota's unique law stems from a murder case that came before the state Supreme Court in 1985. The prosecutor had offered a one-sentence description of the victim in his opening statement, noting that he was a 28-year-old police officer who had grown up in northern Minnesota and had a wife and child. Then the prosecutor "choked up." The judge declared a recess to allow the prosecutor to regain his composure.

The Minnesota Supreme Court ruled that the judge was not required to declare a mistrial and start over. It acknowledged that "the quality or personal details of the victim's life are not strictly relevant." But, it said, "The victim was not just bones and sinews covered with flesh, but was imbued with the spark of life. The prosecution has some leeway to show that spark and present the victim as a human being as long as it is not an 'attempt to invoke any undue sympathy or inflame the jury's passions.' "

Over the years, prosecutors seeking to evoke sympathy and inflame a jury's passions have pushed the door farther open. In one case, a prosecutor was allowed to show that the victim was captain of his high school football team, had a tattoo of his mother on his wrist, tutored young children, wanted to be a teacher and was honored at a tree-planting ceremony.

The problem is not just that such evidence is irrelevant and prejudicial. Often it is also one-sided and misleading. No one wishes to speak ill of a deceased victim, and it would be especially unbecoming for the person accused of the killing to do so. Prosecutors thus can portray flawed victims as saints without much fear of contradiction.

As the Chauvin case illustrates, the law itself may block an evenhanded depiction of a victim's life. The prosecutor in this case reportedly plans to present photographs of George Floyd as a child and at other stages of life. He plans to call Floyd's brother to describe Floyd's childhood, his closeness to his mother and what a good brother he was. The prosecutor also plans to call a witness to give a sympathetic description of Floyd's struggle with drug addiction. (The prosecutor evidently considers it advantageous to acknowledge Floyd's drug problem before the defense attempts to show that drug use caused his death.)

But the jury will not hear about Floyd's criminal record, including the crime of violence that led to his imprisonment for five years.

Floyd's love for his mother and his worst criminal offense are both irrelevant to the issues the Chauvin trial presents. Floyd isn't on trial, and fighting about whether he was a good guy or a bad guy would be an ugly distraction.

As unfortunate as even a "balanced" presentation of George Floyd's life would be, a one-sided presentation would be worse. Critics won't hesitate to ridicule a trial that tells jurors about Floyd's love for his family but not his crimes. An unfair trial seems likely to reinforce the view of those who believe the police are more persecuted than the people some officers mistreat.

George Floyd's criminal record and the unmistakably one-sided character of the evidence the prosecutor wants to present makes Chauvin's case different from the others in which Minnesota courts have allowed "spark of life" evidence. Because Judge Cahill's ruling was tentative, he still could keep it out.

This evidence poses dangers for the prosecutor, too. Judge Cahill warned that going too far — by calling Floyd a "gentle giant" for example — would open the door to evidence that he was not in fact so gentle. Even the evidence the judge indicated he'd allow poses a risk that a conviction would be reversed on appeal.

The prosecutor also can reconsider his decision to present this evidence, and he should.

Albert W. Alschuler, a former federal prosecutor, is the Julius Kreeger Professor Emeritus at the University of Chicago Law School.