What is a federal search warrant?

Federal law enforcement officials obtain search warrants when they need to move quickly on a criminal investigation, or are concerned that sensitive materials they need might be in danger of being moved, concealed, altered or destroyed.

The request for a search warrant is made by a federal law enforcement agency if officials conclude that information, often documents or electronic devices, related to a criminal investigation can be found at someone’s residence, business, car or other property.

A search warrant is not in itself an indication or accusation of the subject’s guilt.

Nonetheless, the use of such a warrant does indicate a sense of prosecutorial urgency — and is used only when “it appears that the use of a subpoena, summons, request, or other less intrusive alternative means of obtaining the materials would substantially jeopardize the availability or usefulness of the materials sought,” according to the Justice Manual, the department’s official guidebook on criminal procedure.

Neither the Justice Department nor the F.B.I. has the authority to act unilaterally. A federal judge or magistrate must approve of the request, and jurists often demand highly specific limitations on the search to protect a person’s Fourth Amendment rights against unlawful search and seizure before granting a warrant.

Law enforcement agencies must meet certain legal benchmarks, litigated over decades, before a judge can sign off.

First, they must prove “probable cause,” evidence that the search is likely to find evidence of illegality; if the warrant is found to lack such proof, the search is considered unlawful under a 2004 precedent.

In addition, the courts have ruled that a search warrant should describe the location and nature of the search with “particularity” — to prevent agents from misusing a warrant to conduct a search that goes beyond the parameters of what has been specifically requested.