In Mendenhall v. Denver, the plaintiff is making an argument about search warrants that could completely change the informant landscape. Police got a warrant to search Michael Mendenhall’s house based on hearsay, which is to say, by repeating something that somebody else said. Mendenhall is represented by the Institute for Justice, and his attorneys are arguing that the warrant violated the plain text of the Fourth Amendment which requires that all warrants be “supported by oath or affirmation.” Since the officer swearing out the warrant had no firsthand knowledge, the argument goes, he could not properly swear to the facts in his affidavit. For this argument to prevail, the Supreme Court would have to overturn Jones v. United States, 362 U.S. 257 (1960), which permitted the issuance of a warrant based on hearsay allegations from an informant. If Mendenhall prevails, police could no longer rely on assertions from confidential informants in order to get warrants. Since the majority of warrants, and the vast majority of drug warrants, rely on informants, this would be a massive change in the law.
Here is a Reason Magazine piece on the case; amicus briefs from law professors and civil rights attorneys can be found on the IFJ page. And here is a law review article by Professor Laurent Sacharoff that explains the historical argument: “The Broken Fourth Amendment Oath,” 74 Stanford Law Review 603 (2022).