The Affidavit Behind a Search Warrant

A search warrant is a short document. The work sits in the affidavit filed with it, a sworn statement that has to persuade a judge of two separate things: that an offense has probably been committed, and that evidence of it will probably be found at the particular place described. Everything a reviewing court later considers is fixed at the moment the affidavit is signed, which is why so much of the litigation about warrants is really litigation about a document nobody expected to be read closely.

What the affidavit must establish

The showing is probable cause: a fair probability, on the totality of the circumstances, that the described items will be found in the described place. It is a practical standard, and it does not require proof by a preponderance. The affiant states facts, and an officer's training and experience may be used to explain what those facts mean, but experience cannot substitute for facts. An affidavit consisting of conclusions and professional opinion, with no underlying observation, gives the magistrate nothing to decide.

Particularity is the second constitutional requirement and it is set out in the warrant rather than the affidavit, though the affidavit usually supplies the description. The place must be described so that an executing officer can identify it with reasonable effort and cannot mistakenly search another. The things must be described so that discretion at the scene is limited to what is authorized. A warrant listing records and other evidence of criminal activity, without confining the category to a stated offense, is the classic general warrant problem.

Review is confined to the four corners of the affidavit. Information an officer possessed but did not put in writing does not count, however compelling it later proves to be, and testimony at a suppression hearing cannot fill a gap that existed when the warrant issued. The one recognized supplement is sworn oral testimony given to the issuing judge, which counts only if the judge placed the applicant under oath and made a record of it. Rule 41 accommodates that by permitting applications by telephone or other reliable electronic means with the testimony recorded.

Nexus to the place and stale information

Nexus is the requirement most often missed, because an affidavit can establish overwhelming grounds to believe a person committed an offense and still say nothing about the residence. Probable cause as to a person is not probable cause as to that person's home. The affidavit must supply a link — deliveries observed at the address, records tying the account to the premises, statements about where material is kept — or an inference courts accept, such as the tendency of certain categories of evidence to be kept where the person lives. Circuits differ on how far that inference stretches, and it is weakest where the offense is a single transaction elsewhere.

Staleness asks whether the information still supports a present belief. There is no fixed interval. What matters is the nature of the items and the character of the activity: a firearm, a business record or a stored digital file is expected to remain, while a consumable quantity of a controlled substance is expected to be gone. Ongoing conduct refreshes older information. An affidavit that omits when the events occurred creates a staleness problem of its own, since the magistrate cannot assess currency at all.

Informants and the totality approach

Where the facts come from a source rather than from the affiant's own observation, three considerations are weighed: the informant's veracity, the informant's reliability, and the basis of knowledge. These were once rigid prongs, each of which had to be satisfied independently. The Supreme Court replaced that structure with a totality approach in which a deficiency in one may be compensated by a strong showing on another. A detailed firsthand account can carry a source whose track record is unknown; a long history of accurate reports can carry an account short on detail.

Corroboration is what usually does the work. An affidavit that recites innocuous details officers independently confirmed — a vehicle, an address, a pattern of movement — supports an inference that the source is equally accurate about the parts that could not be checked. An anonymous tip standing alone rarely suffices. A named citizen reporting a firsthand observation is treated more favorably, since that informant is exposed to consequences for a false report. A source paid or working off a charge is neither disqualified nor presumed unreliable, though the arrangement should appear in the affidavit.

The magistrate and a challenge to the affidavit

The warrant must issue from a neutral and detached magistrate. Judicial office is not the test. A magistrate has been held not neutral where compensation depended on issuing warrants, and where the issuing officer left the bench to accompany and direct the search. The requirement also fails where a magistrate serves as a rubber stamp and performs no independent assessment.

A defendant who believes the affidavit contains a deliberate or reckless falsehood may seek an evidentiary hearing, but only on a substantial preliminary showing. That showing must point to the specific statement claimed to be false, explain why, and be supported by affidavits or a satisfactory explanation of their absence. Even then, no hearing is held unless the challenged material was necessary to the finding of probable cause. If the hearing occurs and the falsehood is proved by a preponderance, the statement is set aside; the warrant fails only if what remains no longer establishes probable cause. The same architecture applies to omissions.

Execution, inventory and delayed notice

Rule 41 governs what happens next. The warrant commands execution within a period not longer than 14 days, during the daytime unless the judge expressly authorizes another time for good cause. The officer must prepare an inventory of any property seized, do so in the presence of another officer and, if present, the person from whom the property was taken, and deliver a copy of the warrant and a receipt to that person or leave them at the place. The inventory is then returned to the judge.

Forced entry has its own statutory condition. An officer may break an outer or inner door to execute a warrant only after giving notice of authority and purpose and being refused admittance. Courts have recognized circumstances excusing announcement where it would be dangerous or futile, or would allow destruction of evidence. A separate statute permits a warrant for property constituting evidence of a federal offense and allows notice of execution to be delayed on a finding of reasonable cause, for a period the court sets and may extend within statutory caps.

Challenges to the affidavit and to the execution are raised together in a pretrial filing, and the court must state its essential findings on the record, which is what makes the ruling reviewable. That procedure appears in the suppression motion and how it is decided. Where no warrant was obtained, the government must fit the search into a recognized exception — consent and who is able to give it, or one of the justifications set out in exigent circumstances and what they excuse. Digital warrants raise their own particularity problems, taken up in searching a phone and what a warrant must say.