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Three years after George Floyd's death, legal developments and new revelations about the case continue to unfold.

Former Minneapolis police officer Derek Chauvin recently appealed his case to the Minnesota Supreme Court. Former officer Tou Thao still awaits sentencing on his state conviction for manslaughter. Prosecution witness Donald Williams has filed suit against the Minneapolis Police Department for emotional distress. And Minnesota Attorney General Keith Ellison's book "Break the Wheel" was just released to the public, recounting his experience leading the prosecution of the Chauvin case.

The Chauvin trial provided a landmark legal decision and Ellison's book offers an interesting insiders perspective. As a criminal litigator for more than 30 years, I watched every minute of the trial and provided local and national legal analysis to the media. Even so, Ellison's narrative still offered me some surprises.

In "Break the Wheel," Ellison discloses that before the Chauvin trial he used several mock juries to test prosecution theories and evidence against the four ex-police officers charged with murdering George Floyd.

Ellison detailed how his team hired a private jury consulting firm to set up three separate groups of mock juries from around the state, including Hennepin County. Ellison writes that "Mocks are an abbreviated form of an actual trial, with opening statements, testimony, presentation of documentary evidence, closing arguments and jury deliberations." He says that he found these juries to be very helpful.

I found this revelation surprising. Mock juries are common in civil cases in Minnesota, but create the potential for a lot of risks in criminal prosecution.

Typically, in civil cases, the use of a mock trial is considered attorney "work product" for trial preparation purposes, which is generally not discoverable by the opposing side. In criminal cases, however, prosecutors bear an additional obligation — the affirmative duty to disclose to the defense any evidence that is favorable to the defendant. This obligation in our criminal justice system is commonly referred to as the "Brady rule," as it is based on the U.S. Supreme Court's 1963 decision Brady v. Maryland.

There are a few significant reasons mock trials present risks to a prosecution.

First, Minnesota law places a greater duty on prosecutors to make disclosures to defendants than does the law in most states. If mock trials were not disclosed to the defendant in a case, there could be a violation of discovery rules. Mock trials are like trial experts — both can potentially produce findings and opinions after reviewing the evidence, and prosecutors must disclose such opinions to the defense.

Second, in any criminal case, the prosecutor should notify the defense if they used a mock jury before the actual criminal trial in question begins. Imagine if the jury pool in a criminal trial contained a potential juror who was in on one of the prosecutor's mock juries or knew someone who was on a mock jury. Such experience or communication could easily affect the juror's ability to be fair and impartial.

In Chauvin's trial, all potential jurors completed a 10-page juror questionnaire that contained 37 questions, but there were no questions pertaining to mock juries.

Finally, a mock trial could violate the Minnesota Data Practices Act (MDPA). The MDPA prohibits public disclosure of criminal investigative materials (witness statements, police reports, forensic tests, recordings, medical examiner reports, etc.) until the criminal case in question is concluded. Providing such materials to mock jurors could amount to a violation of the MDPA, which could lead to other legal problems and appeals.

Ellison's successful prosecution of the four ex-police officers has set an example for many in how to investigate and criminally try excessive use of force cases. Ironically, however, extolling the benefits of using mock juries in that prosecution could provide the ex-officers with new avenues of appeal (motions for new trials) and create new legal grounds for criminal defense attorneys to obtain prosecutorial work product in future cases.

"Break the Wheel" will have a social and literary impact, but its unintended consequence could be the creation of more serious challenges for all prosecutors.

Joe Tamburino is an attorney in Minneapolis.