Motion to Suppress: How to Research and Write One (Fourth Amendment, Miranda, Franks)

A motion to suppress asks the court to exclude evidence the government obtained unconstitutionally: through a search or seizure that violated the Fourth Amendment, a custodial interrogation that violated Miranda, or questioning that violated the right to counsel. In federal court it must be filed before trial.

This article is for general information and is not legal advice. For guidance on a specific case, consult a licensed attorney in your jurisdiction.

Defendants and families reading this should know that suppression turns on the facts of one stop, warrant or interview and on the law of one jurisdiction. Nothing here predicts how any motion will come out.

The three grounds for a motion to suppress

Mapp held that "all evidence obtained by searches and seizures in violation of the Constitution is, by that same authority, inadmissible in a state court," which made the exclusionary rule binding on the states. 367 U.S. at 655. Miranda barred the prosecution from using statements "stemming from custodial interrogation of the defendant unless it demonstrates the use of procedural safeguards effective to secure the privilege against self-incrimination." 384 U.S. at 444.

A Fourth Amendment motion begins with a threshold question: whose rights were violated? Fourth Amendment rights "may not be vicariously asserted," and the defendant must show his own legitimate expectation of privacy in the place searched. Rakas v. Illinois, 439 U.S. 128 (1978). The passengers there lost because they claimed no privacy interest in the glove compartment or the area under the seat. Make that showing in the motion; do not wait for the government to raise it.

The federal deadline: Rule 12(b)(3)(C)

Fed. R. Crim. P. 12(b)(3) lists "defenses, objections, and requests" that "must be raised by pretrial motion if the basis for the motion is then reasonably available and the motion can be determined without a trial on the merits." Item (C) is "suppression of evidence." Rule 41(h) points the same way: "A defendant may move to suppress evidence in the court where the trial will occur, as Rule 12 provides."

• Deadline. Under Rule 12(c)(1), the court "may, at the arraignment or as soon afterward as practicable, set a deadline for the parties to make pretrial motions and may also schedule a motion hearing. If the court does not set one, the deadline is the start of the trial."
• Late motions. Under Rule 12(c)(3), a missed deadline makes the motion untimely, but "a court may consider the defense, objection, or request if the party shows good cause."
• Findings. Under Rule 12(d), "[w]hen factual issues are involved in deciding a motion, the court must state its essential findings on the record."

Treat the scheduling order as the real deadline. In state court, check your own rules rather than assume the federal pattern.

Who has the burden

The defendant carries the threshold burden of showing a protected interest in the place or thing searched. Rakas, 439 U.S. at 130-31 n.1. Beyond that, many courts require the government to justify a warrantless search by showing an exception to the warrant requirement, while in warrant cases the defendant usually carries the burden of showing the warrant was defective. That pattern varies, so confirm the burden rule in your circuit's or state's controlling authority before you frame the facts. Finding controlling authority covers that step; binding versus persuasive authority covers what to do when your circuit has not ruled.

The exceptions the government will raise

Proving a violation is half the work. The government has four standard routes to keep the evidence in, each its own research task.

Fruit of the poisonous tree. The governing test comes from Wong Sun. The question is "whether, granting establishment of the primary illegality, the evidence to which instant objection is made has been come at by exploitation of that illegality or instead by means sufficiently distinguishable to be purged of the primary taint." 371 U.S. at 488.

Good faith. Leon held that evidence obtained by officers acting in objectively reasonable reliance on a warrant issued by a neutral magistrate need not be excluded from the prosecution's case in chief. The decision names situations where suppression remains appropriate: the magistrate was misled by an affidavit the affiant knew was false or would have known was false but for reckless disregard of the truth; the magistrate wholly abandoned the judicial role; the affidavit was "so lacking in indicia of probable cause as to render official belief in its existence entirely unreasonable"; or the warrant was so facially deficient, as in failing to particularize the place to be searched or the things to be seized, that officers could not reasonably presume it valid. Those four categories are also your checklist for attacking a warrant.

Inevitable discovery. The evidence comes in if the government "can establish by a preponderance of the evidence that the information ultimately or inevitably would have been discovered by lawful means." Nix, 467 U.S. at 444. It needs a concrete lawful path, not speculation. In Nix the path was a volunteer search party already approaching the body.

Independent source. Evidence first seen during an unlawful entry can still come in if it was later obtained through a genuinely independent lawful source, such as a later warrant. Under Murray, the warrant search is not independent if "the agents' decision to seek the warrant was prompted by what they had seen during the initial entry," or if information from that entry "was presented to the Magistrate and affected his decision to issue the warrant." 487 U.S. at 542. Attack both prongs.

Attenuation. Strieff applied the Brown v. Illinois factors, which ask about temporal proximity, intervening circumstances, and the purpose and flagrancy of the official misconduct. A 5-3 Court held that a pre-existing, valid arrest warrant discovered during an unlawful stop attenuated the connection to the evidence found in the search incident to arrest. Distinguish your facts on the intervening event and on flagrancy.

Franks hearings: attacking the affidavit

If the problem is in the warrant affidavit rather than the search itself, the vehicle is Franks v. Delaware, 438 U.S. 154 (1978). A hearing is not automatic. The defendant must make "a substantial preliminary showing that a false statement knowingly and intentionally, or with reckless disregard for the truth, was included by the affiant," and the statement must be "necessary to the finding of probable cause." 438 U.S. at 155-56.

Franks recognizes a presumption that the affidavit is valid, and the challenge "must be more than conclusory and must be supported by more than a mere desire to cross-examine." It also requires an offer of proof: "Affidavits or sworn or otherwise reliable statements of witnesses should be furnished, or their absence satisfactorily explained." 438 U.S. at 171. A motion that says "the officer lied" without a sworn source gets no hearing.

Write the Franks section in this order: identify the specific statement, state what the evidence shows is true, explain why the officer knew or recklessly disregarded it, and show that probable cause fails once the falsehood is removed. Attach the declarations. Then check the Leon exception, because an affidavit the affiant knew was false is the first category where good faith is unavailable.

Miranda fruits are different

Do not carry fruit-of-the-poisonous-tree reasoning over to Miranda motions. The Fourth Amendment taint doctrine is broad; the Miranda version is narrower.

• In United States v. Patane, 542 U.S. 630 (2004), a three-Justice plurality held that a failure to give Miranda warnings does not require suppression of the physical fruits of a suspect's unwarned but voluntary statements; two more Justices concurred in the judgment.
• In Oregon v. Elstad, 470 U.S. 298, 318 (1985), the Court held that "a suspect who has once responded to unwarned yet uncoercive questioning is not thereby disabled from waiving his rights and confessing after he has been given the requisite Miranda warnings."

Both turn on the statement being voluntary. If you can show actual coercion, you argue a due process voluntariness claim, and the tainted-fruit reasoning is stronger. The unwarned statement itself is a separate matter and is generally unavailable to the government in its case in chief if the Miranda violation is established. Confirm current law in your circuit on two-step interrogation practices before you rely on Elstad in either direction.

Appeal: build the record first

On appeal from a federal suppression ruling, "determinations of reasonable suspicion and probable cause should be reviewed de novo," while a reviewing court should "review findings of historical fact only for clear error and ... give due weight to inferences drawn from those facts by resident judges and local law enforcement officers." Ornelas v. United States, 517 U.S. 690, 699 (1996). That de novo rule covers warrantless stops and searches; a magistrate's decision to issue a warrant gets more deference. Id. at 698-99.

In practice, the trial court is the last fact-finder in most cases, and clear-error review rarely rescues a thin record. Put the video, the dispatch log and the officer's prior statements into evidence at the hearing. Ask for specific findings under Rule 12(d).

How to write a motion to suppress: a research checklist

1. Standing. Pull your jurisdiction's cases on the interest at stake (home, car, phone, cloud account, rental).
2. The search or stop. Find controlling authority on the exact exception the government will invoke: consent, exigency, search incident to arrest, automobile, plain view, inventory.
3. The warrant. Read the affidavit line by line. List every statement you can contradict. Pull Franks cases from your circuit.
4. The exceptions. For each of the four, find the circuit's test and the cases where it failed.
5. The statement. Establish custody, interrogation, warnings and waiver separately.
6. Newer technology. Digital-device and location-data law moves quickly. Check recent decisions in your circuit, and set up a monitor if you handle these motions regularly.
7. Good law. Check every case for later treatment. See how to check if a case is still good law.

A motion to suppress asks the court to exclude unlawfully obtained evidence and is decided before trial. A motion in limine asks for a ruling on admissibility under the rules of evidence and is usually made close to trial. A defective indictment is attacked by its own pretrial motion under Rule 12(b)(3)(B); the civil motion to dismiss is a different tool.

Frequently asked questions

What is a motion to suppress?

A motion to suppress asks the trial court to exclude evidence the government obtained in violation of the defendant's constitutional rights, usually through an unlawful search or seizure under the Fourth Amendment, a custodial interrogation without Miranda warnings, or questioning after the right to counsel attached. If it is granted, the prosecution cannot use the evidence in its case in chief at trial, though it may sometimes use it for other purposes, such as impeachment.

When must a motion to suppress be filed in federal court?

Before trial. Federal Rule of Criminal Procedure 12(b)(3)(C) requires a motion to suppress evidence to be raised pretrial if the basis is then reasonably available. The court may set a deadline at arraignment or soon after; absent one, the deadline is the start of trial. A late motion is considered only on a showing of good cause. State deadlines vary by jurisdiction.

What is a Franks hearing?

A Franks hearing is an evidentiary hearing on whether a search warrant affidavit contained a deliberate or reckless falsehood. Under Franks v. Delaware, a defendant must first make a substantial preliminary showing, supported by an offer of proof, that a false statement was knowingly or recklessly included and was necessary to probable cause. The hearing is not automatic, and conclusory allegations do not earn one.

Does fruit of the poisonous tree apply to Miranda violations?

Not in the same way it applies to Fourth Amendment violations. In United States v. Patane, a plurality held that failing to give Miranda warnings does not require suppression of the physical fruits of a voluntary, unwarned statement. Oregon v. Elstad similarly allows a later, properly warned statement after an earlier voluntary unwarned one. The unwarned statement itself is still generally inadmissible in the government's case.

What is the standard of review when a suppression ruling is appealed?

In federal court, ultimate determinations of reasonable suspicion and probable cause for a warrantless stop or search are reviewed de novo on appeal, while findings of historical fact are reviewed only for clear error, with due weight to inferences drawn by resident judges and local officers. A magistrate's decision to issue a warrant gets more deference.

Before you file it

The government's response to a suppression memorandum will test every authority in it. CaseRead can research circuit and state authority scoped to your matter. Run the finished draft through the Hallucination Shield: free, no signup, and each citation it finds (up to 50 per run) is checked for existence. It flags citations it cannot verify; it does not judge whether you described a holding correctly, so the quote-and-pincite pass in how to cite check a brief still applies, as does verifying any AI-generated citations.

This article is for general information and is not legal advice. For guidance on a specific case, consult a licensed attorney in your jurisdiction.