Warrant 101: What Makes a Search Warrant Legitimate?

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A search warrant is a judge’s permission to search a particular place. The Fourth Amendment sets the test for a legitimate one: it must rest on probable cause, be backed by an oath or affirmation, and name the specific place to search and the persons or things to seize.

Probable cause means a fair probability, judged from all the circumstances, that contraband or evidence of a crime will be found in that place. It is not a finding that anyone is guilty. The decision belongs to a neutral decisionmaker, not the police or prosecutors running the investigation. A search warrant can be legitimate even when the person whose home is searched is not suspected of a crime.

What a search warrant authorizes

A search warrant is judicial permission based on probable cause that the legitimate object of the search is in a particular place. An arrest warrant instead rests on probable cause that its subject committed an offense, protecting against an unreasonable seizure of that person.

Under the Federal Rules of Criminal Procedure, Rule 41, a search warrant may concern crime evidence, contraband (illegally possessed items), property used or intended for a crime, or a person to be arrested or unlawfully restrained.

The Fourth Amendment’s protections apply to the states through the Fourteenth Amendment. So the constitutional requirements bind state and local police too, but the federal procedural details below should not be assumed to be the rule for a state search.

Probable cause must connect evidence to the place

The issuing decisionmaker must be neutral and detached, because police and prosecutors cannot provide the required neutrality toward their own investigations. A federal officer or government attorney seeking a warrant may present an affidavit, a written statement made under oath, in support. The judge may examine the affidavit’s author under oath or, when reasonable, rely wholly or partly on sworn testimony instead of a written affidavit.

The probable-cause test asks whether all the circumstances show a fair probability that contraband or crime evidence will be found in the particular place. It does not require the proof beyond a reasonable doubt used in a criminal trial.

In Illinois v. Gates, decided June 8, 1983, police received an anonymous letter on May 3, 1978, saying a husband and wife were selling drugs, then checked the couple’s address and the husband’s flight reservation. Surveillance confirmed that he took the flight, stayed at a motel registered in his wife’s name and left in their Illinois-registered car. Those checks gave the judge more to evaluate than an unsupported accusation in a letter.

The Supreme Court concluded that the issuing judge had a substantial basis to find probable cause to search the home and car. The court reaffirmed that probable cause is judged on the totality of the circumstances, with an informant’s truthfulness and basis of knowledge weighed as part of the whole.

The central connection is reasonable cause to believe that the specific things sought are on the property, not whether the property owner is suspected of a crime. Suppose the only evidence offered is a photograph of someone with a felony record. By that test it is not enough simply because it identifies the person; what matters is what the photograph shows and whether it connects the things sought to the place to be searched.

The proof supporting a warrant must relate to the time it is issued, with older information updated or supplemented when necessary to establish probable cause then. Information that established a reason to search earlier does not automatically establish that the same evidence remains there later.

What the warrant must say

The Fourth Amendment requires the warrant to describe the place to be searched particularly. A tracking-device warrant authorizes using a device to track a person or property and may also authorize installation. Except for a tracking-device warrant, a federal search warrant must identify the person or property to search, the person or property to seize and the magistrate judge, a judicial officer of a federal district court, to whom it must be returned. Those descriptions connect the judge’s permission to an identifiable search rather than leaving officers to choose its subject after entry.

An authorization to seize “evidence of crime” can be so open-ended that it amounts to a general warrant, one with no real limit on what may be taken. In Groh v. Ramirez (2004), the application adequately described the things to be seized, but the warrant itself did not. The Supreme Court held that the application did not save the warrant: the warrant incorporated no other documents, and neither the affidavit nor the application accompanied it.

A warrant to search a home for illegal weapons permits opening closets, chests, drawers and containers where a weapon might be found. The thing being sought sets that limit: a space too small to hold it is a different matter from a container that could.

Whose property and which court matter

A search warrant may cover a third party’s property when there is probable cause that crime evidence will be found there, even if the occupant is not suspected of wrongdoing. That rule does not settle every search for materials held by a journalist or publisher. The Privacy Protection Act generally prohibits search warrants for work product and other documentary materials held by someone reasonably believed to be planning to publish a newspaper, book, broadcast or similar public communication.

Documentary materials are recorded information, such as writings, photographs and recordings; work product is material prepared and held for public communication that includes its creator’s mental impressions, conclusions, opinions or theories. Both definitions exclude contraband, items obtained through crime, other illegally possessed items and property designed, intended or used to commit a crime.

The act allows a warrant when there is probable cause that the person holding the materials committed a crime to which they relate. That exception does not apply when the alleged crime is itself the receipt, possession, communication or withholding of the materials or the information in them, unless the offense involves classified materials or child pornography. A warrant is also allowed when there is reason to believe immediate seizure is necessary to prevent death or serious bodily injury.

For documentary materials that are not work product, there are two more exceptions. One applies when there is reason to believe that giving notice through a subpoena, a formal demand for the documents, would lead to their destruction, alteration or concealment. The other applies when those documents have not been produced in response to a court order enforcing a subpoena and either all appeals are exhausted or further delay would threaten the interests of justice.

Whether an arrest warrant lets officers search another person’s home is a separate question. An arrest warrant carries limited authority to enter the suspect’s own dwelling when there is reason to believe the suspect is inside. In Steagald v. United States, decided April 21, 1981, federal drug agents entered a resident’s home with an arrest warrant for someone else, without first obtaining a search warrant. Agents found incriminating evidence but not the wanted person, and the resident was convicted after the trial court refused to exclude the evidence from his trial.

The Supreme Court held that searching a third party’s home for an arrest-warrant subject requires a search warrant absent consent or emergency circumstances. It reversed the appeals court judgment that had affirmed the conviction. The arrest warrant addressed the wanted person’s liberty, while the missing search warrant concerned the resident’s privacy.

Which court can issue a warrant depends on where the search will take place. For an ordinary federal search, Rule 41 allows a magistrate judge with authority in the district to issue a warrant for a person or property within that district. If no federal magistrate judge is reasonably available, a state court-of-record judge in that district may issue it. A court of record keeps a permanent record of its proceedings. A federal law enforcement officer or government attorney requests the warrant, which is issued to an officer authorized to execute it.

Under 28 U.S.C. § 566(c), the U.S. Marshals Service executes lawful federal writs, process and orders, except as otherwise provided by law or procedural rule. A writ commands a specific act; process includes writs, summonses and orders used in a case; an order gives written directions from a court or judge. For an ordinary federal search warrant, including one that U.S. marshals carry out, the question under Rule 41 is whether the person or property is located within the district of the judge who issued it, not which county it is in.

Rule 41 also provides an exception for terrorism investigations, allowing a magistrate in a district with related activities to authorize a search inside or outside that district.

Officers still face limits when they search

Apart from tracking-device warrants, a federal search warrant must direct officers to carry it out within a specified time, no longer than 14 days. For electronic information, that execution period concerns seizure or on-site copying, not later off-site copying or review.

Rule 41 defines daytime as 6:00 a.m. to 10:00 p.m. local time. Under that rule, a search outside daytime requires the judge’s express authorization for good cause.

Federal law, 18 U.S.C. § 3109, permits an officer to break open a door or window of a house to execute a search warrant if the officer has announced his or her authority and purpose and been refused entry. It also permits breaking a door or window when necessary to free the officer or someone helping carry out the warrant. The Supreme Court has said that to skip knocking and announcing, police need reasonable suspicion that knocking and announcing in the particular circumstances would be dangerous or futile, or would hinder the investigation, such as by allowing evidence to be destroyed.

For a federal search, the officer must give the affected person a copy of the warrant and a receipt for property taken, or leave them where the property was taken. For a warrant to search electronic storage media by remote access, the officer must make reasonable efforts to serve the copy and receipt by means reasonably calculated to reach the person. As written, that rule covers delivering the documents; it does not say the person must receive them before the search begins.

The federal rule also requires an officer to prepare and verify an inventory of seized property in the presence of another officer and the affected person, or at least one other credible person if either is absent. The warrant and a copy of that inventory must be promptly returned to the designated magistrate judge.

A warrant for contraband founded on probable cause includes limited authority to detain occupants of the premises while a proper search is conducted. But a person’s presence near someone suspected, or on premises covered by a warrant, does not itself provide individualized probable cause to search that person.

Consent and emergency circumstances are recognized exceptions to the requirement for a warrant to search a home. The absence of a warrant therefore does not by itself make a search unlawful.

An unlawful search does not guarantee one remedy

The exclusionary rule enforces the Fourth Amendment by keeping unconstitutionally gathered evidence out of trial, in state courts as well as federal ones. Under the Supreme Court’s 1984 decision in United States v. Leon, suppression, the exclusion of evidence, may be inappropriate when officers reasonably rely on the issuing judge’s probable-cause determination and the warrant’s technical sufficiency.

Good-faith reliance does not protect a knowingly or recklessly misleading affidavit, an issuing official who abandons the neutral role, an affidavit that unreasonably lacks signs of probable cause, or a warrant so facially deficient that officers cannot reasonably presume it valid. A defendant can obtain a hearing by making a substantial preliminary showing that the affidavit included a knowingly or recklessly false statement that was necessary to the probable-cause finding.

In its 2006 decision in Hudson v. Michigan, the Supreme Court held that a knock-and-announce violation does not require suppression of the evidence found in the search.

Fourth Amendment rights are personal and generally cannot be asserted on someone else’s behalf. A federal criminal defendant may move to suppress evidence in the court where the trial will occur, as Rule 12 of the same federal rules provides. Rule 12 of the Federal Rules of Criminal Procedure covers pleadings and pretrial motions, including requests to suppress evidence.

A person seeking return of property under Rule 41(g) files in the district where it was seized; a court granting return may impose reasonable conditions protecting later access and use.