U.S. Supreme Court justices appeared torn Wednesday over whether prosecutors deserve total immunity from lawsuits for their official acts, even when they fabricate evidence in pursuit of a murder indictment and conviction.

The Court heard arguments in Pottawattamie County v. McGhee and Harrington, brought by two men who were freed after serving 25 years in prison for murdering a retired Iowa policeman. Based on recently obtained police files, Curtis McGhee and Terry Harrington sued prosecutors for violating their civil rights by coercing and coaching witnesses to falsely accuse them of the crime, even when evidence pointed toward another suspect.