The single most powerful tool available to a criminal defendant whose property has been searched is the motion to suppress evidence obtained in violation of the Fourth Amendment or its Michigan constitutional analogue. Under the exclusionary rule established in Mapp v Ohio, 367 US 643 (1961), evidence obtained through an unconstitutional search is inadmissible at trial. In Michigan, the exclusionary rule operates through motions filed under MCR 6.311 and through the court's inherent supervisory authority. The grounds for suppression are numerous and technically demanding—which is why early retention of experienced defense counsel is essential after a search warrant is executed.

The most fundamental ground for suppression is the absence of probable cause in the warrant affidavit. The affidavit must contain facts within the knowledge of the affiant, and any informant information relied upon must be evaluated for both the informant's credibility and the reliability of the information, as codified in MCL 780.653 and interpreted through the Aguilar-Spinelli framework that Michigan continues to apply. People v Hawkins, 468 Mich 488 (2003). Where the affidavit contains knowingly or recklessly false statements, the defendant may challenge the affidavit's veracity under the standards established in Franks v Delaware, 438 US 154 (1978), and adopted in Michigan. People v Franklin, 500 Mich 92 (2017) confirmed that Michigan trial courts retain discretion to conduct evidentiary hearings on the veracity of warrant affidavits even without the substantial preliminary showing formally required by Franks. Defense counsel should request such hearings whenever the affidavit contains factual averments that appear questionable or that can be contradicted by the defendant's own records or witnesses.

Staleness of the information in the affidavit is a separate and frequently overlooked ground for challenging a warrant. Michigan law requires that probable cause must exist at the time the warrant is issued, not at some earlier point. People v Broilo, 58 Mich App 547 (1975). In evaluating whether information has become stale, courts consider the nature of the crime, the character of the criminal, the perishability and utility of the items to be seized, and whether the place to be searched is a secure operational base for the criminal activity. United States v Frechette, 583 F3d 374 (CA 6, 2009). Where weeks or months have passed between the events described in the affidavit and the warrant's issuance, the defense should scrutinize the staleness question carefully.

Even a facially valid warrant may result in an unlawful search if the officers exceed its scope during execution. Michigan v Summers, 452 US 692 (1981), confirmed that a warrant to search premises carries limited implicit authority to detain occupants during the search, but does not authorize a full search of those occupants unless independent probable cause exists. People v Arterberry, 431 Mich 381 (1988), addressed the circumstances under which contraband discovered during a premises search provides probable cause to arrest and search an occupant not named in the warrant. Defense counsel must carefully compare the scope of the warrant's description of items to be seized against the inventory of items actually seized, which must be provided to the owner under MCL 780.655, to identify any items seized outside the warrant's authority.

The invalidity of a portion of a search warrant does not necessarily require suppression of all evidence seized. Under the severance doctrine, trial courts sever the tainted portions of a warrant from the valid portions and apply suppression only to items seized under the invalid provisions. People v Kolniak, 175 Mich App 16 (1989). This principle requires that defense counsel analyze each seized item against the warrant's provisions to determine which items fall within the valid portions and which do not. The remedy of complete suppression—excluding all seized evidence—is available when the entire warrant lacked probable cause or when the defect so permeates the warrant that the tainted and valid portions cannot be meaningfully separated.