The Effect of No-Knock Warrant Restrictions on Admission of Evidence in Federal Court

By Jonathan Knowles

On April 10, 2021, the Maryland legislature overrode Governor Hogan’s veto to pass three bills dedicated to police reform.[1]  Among the provisions contained in these bills were significant restrictions on police officers’ authority to request a “no-knock search warrant.”  Since the tragic death of Breonna Taylor, other states have implemented similar restrictions and more are likely to do so in future.  It is up to the state legislature and courts to determine whether evidence derived from such warrants is admissible in state courts.  If the state decides that it is not, though, does that material also become inadmissible in federal court?

States Are Increasing the Restrictions on No-Knock Warrants

Generally, before entering a building to execute a search warrant or arrest warrant, police officers must inform its occupants that they are police officers and request entry.  Most states, however, permit a judge to excuse the so-called “knock-and-announce” requirement.  Warrants granting leave to disregard this requirement are commonly referred to as “no-knock” warrants.

Maryland’s new law, which takes effect on October 1,[2] will narrow the circumstances under which police officers may seek no-knock search warrants.  The law requires that a request for a no-knock warrant be approved in writing by a police supervisor and the state’s attorney, that the police officers be properly trained in such procedures, and that the application contain other information intended to ensure judges will approve such requests only when doing so is both safe and necessary.[3]  It also requires that such warrants be executed between 8 a.m. and 7 p.m., absent exigent circumstances.[4]

Maryland is not alone in this respect.  Kentucky, Ms. Taylor’s home state, also passed legislation in April that would limit the availability of no-knock warrants.[5]  Since March, Virginia has banned such warrants entirely.[6]  Other states have considered similar measures.[7]  Some local governments have also imposed restrictions.  The most prominent example is Louisville, Kentucky, which banned no-knock warrants last year after the death of Breonna Taylor.[8]

Opposition to no-knock warrants is not, however, an entirely new attitude.  Even before Ms. Taylor was killed, Oregon did not permit judges to authorize unannounced entry while executing a search warrants,[9] although it permits such authorization for arrest warrants.[10]  At least two other states have long prohibited, by statute, unannounced entry to a dwelling by law enforcement.[11]  In practice, however, even states that codify the knock-and-announce rule tend to permit unannounced entry under certain circumstances.[12]

A prohibition on unannounced entry doesn’t necessarily call for the exclusion of evidence.  Since 2006, when the legal framework changed significantly,[13] Maryland courts have not excluded evidence for violation of the knock-and-announce rule (although the State’s highest court has yet to consider the post-2006 framework).[14]  Many states have reached the same conclusion.[15]  Other states, however, have decided differently.  Some suppress evidence obtained from improper no-knock searches or arrests under the constitution of the state.[16]  Florida and Alaska, which have statutory knock-and-announce requirements, have held that the remedy for violation of these requirements is exclusion of the evidence obtained from the unlawful entry.[17]  Virginia’s recent statute expressly provides for suppression, in state court, of evidence derived from no-knock execution of a warrant.[18]

The Fourth Amendment Doesn’t Mandate Suppression for Failure to Knock-and-Announce While Executing a Search Warrant

Until 1960, evidence was inadmissible in federal court only if it had been obtained by federal wrongdoing.  There were no grounds for exclusion “if evidence secured by state authorities is turned over to the federal authorities on a silver platter,”[19] however the state authorities had secured that evidence.  This changed when, in Elkins v. United States, [20] the Supreme Court applied the exclusionary rule to evidence obtained through violations of the Fourth Amendment purely by state officials.  At the time, it was widely understood that the Fourth Amendment included the common-law require that law enforcement officers announce their presence.[21]

This understanding began to change over the ensuing decades.[22] In 1995, the Supreme Court held that a police officer’s unannounced entry of a home could violate the Fourth Amendment, but “[t]his is not to say . . . that every entry must be preceded by an announcement.”[23] The Court did not explain at length when no-knock warrants were permitted under the Fourth Amendment holding only that law enforcement interests may be sufficient to justify entry without a prior announcement.[24] Two years later, the Court put these words into action, affirming a conviction over the defendant’s objection to police officers’ unannounced entry.[25] The Court held that unannounced entry required “a reasonable suspicion that knocking and announcing their presence, under the particular circumstances, would be dangerous or futile, or that it would inhibit the effective investigation of the crime . . . .”[26] This showing, which was “not high,” was met by the defendant’s recognition of the police officers and the easily disposable nature of the possessed drugs.[27]

Finally, in Hudson v. Michigan, the Supreme Court considered whether suppression was the appropriate remedy for violation of the knock-and-announce requirement.[28]  Justice Scalia wrote for the Court that the evidence was obtained because of the valid warrant, not the improper execution of that warrant.[29]  Justice Scalia also wrote that the interests protected by the knock-and-announce requirement did not include preventing the government from seizing evidence.[30]  Finally, he wrote that the costs of suppressing evidence outweighed the benefits of doing so.[31]  Therefore, the Court held that suppression is not warranted where unannounced execution of a search warrant violates the Fourth Amendment.

Does State Law Provide for Federal Suppression?

Violation of the knock-and-announce rule is not necessarily a violation of the Fourth Amendment.  Moreover, even an unconstitutional violation of the rule may not be grounds for excluding evidence from federal court.[32]  Since Hudson, there have been surprisingly few cases analyzing the application of state knock-and-announce statutes in federal court.  The question, then, is whether such laws would call for suppression.

There remains a clear legal argument for the suppression of evidence derived from improper execution of an arrest warrant.  The Supreme Court has not held that the exclusionary rule does not apply to violation of the knock-and-announce rule in the execution of an arrest warrant.  At least one federal court of appeals has held that the privacy interests protected by the rule in the context of an arrest warrant, and the deterrent value in excluding evidence obtained in violation of that rule, are so much stronger in the context of an arrest warrant that suppression of evidence is an appropriate remedy.[33]  The Supreme Court has also implied that a search incident to an arrest must be valid under the Fourth Amendment and state law to be admissible in federal court,[34] although more recent dictum calls this assertion into question.[35]  The Court of Appeals for the Fourth Circuit, which rules on appeals from federal courts in Maryland and Virginia, has not ruled on whether search and arrest warrants should be treated differently under Hudson.  The Virginia and Maryland laws are superficially restricted to search warrants, however, so may not be interpreted as prohibiting no-knock arrest warrants.

For a search warrant, at least in Virginia and Maryland, the superficial answer is no.  The Federal Rules of Evidence provide that evidence is admissible unless provided otherwise by the Rules themselves, the U.S. Constitution, other rules prescribed by the Supreme Court, or a federal statute.[36]  The Court of Appeals for the Fourth Circuit has specifically held that suppression of evidence in federal court is controlled by the Fourth Amendment, not by state law.[37]  It reiterated that holding only two years ago.[38]  Indeed, the Court of Appeals has specifically held that violation of a Virginia statute providing for suppression of evidence would not affect the admissibility of evidence in federal court.[39]  In light of Hudson, this suggests that state law would not prevent the introduction of unlawfully obtained evidence in federal court.

Yet this answer is deeply unsatisfying, as a matter of both law and policy.  Although theoretically the reverse of the ‘silver platter’ doctrine rejected in Elkins, the practical result is the same:  state officials are able to evade limits on their authority by turning over unlawfully obtained evidence to federal prosecutors.  Even Justice Frankfurter, dissenting in Elkins, would have suppressed in federal court evidence that would have been excluded under the laws of the states where the evidence was seized.[40]  This outcome is all the more troubling given the significant expansion of federal criminal law since Elkins.  For example, 16,829 persons were convicted of drug crimes in fiscal year, constituting more than a quarter of all federal convictions.[41]  The number of drug convictions in fiscal year 2019 was even higher, both in absolute terms and as a proportion of federal convictions.[42]  The basis for modern federal drug laws is the Controlled Substances Act, which was passed 10 years after Elkins was decided.[43]

As a matter of law, it is strange to extend a holding that states may choose not to exclude evidence so as to prohibit states from preventing the admission of unlawfully obtained evidence against their citizens.  Fortunately, admission of evidence is not the inevitable result of Hudson.  The Supreme Court’s reasoning in Hudson presupposed that unannounced entry was an improper execution of an otherwise valid warrant, which would have resulted in the seizure of evidence regardless of whether or not the police officers announced themselves.[44]  This premise will not be true where a no-knock warrant is itself invalid under state law.  State law restricting no-knock warrants will also significantly change the cost-benefit analysis of suppressing evidence.  The Court reasoned that the deterrence benefits of suppression were minimal, and outweighed by the social costs, because incriminating evidence could only be obtained under circumstances that permitted unannounced entry.[45]  This is not true where state law restrictions on unannounced entry are more stringent than the restrictions imposed by the Fourth Amendment.  It is also difficult to see how encouraging compliance with recent legislation could be considered a “social cost.”

Regardless, this problem could be resolved by the other branches of the federal government.  Theoretically, the Executive Branch could refuse to introduce any such evidence obtained in violation of state law.  Such a policy would be difficult to enforce, however, and would also be subject to change with each administration.  A better solution would be for Congressional legislation to prevent the admission of such evidence in the courts of the United States.

[1] Bryn Stole & Pamela Wood, Maryland Legislators Pass Landmark Police Reform Package into Law, Overriding Gov. Hogan’s Vetoes, The Baltimore Sun (Apr. 10, 2021),

[2] Anton’s Law, S.B. 178, 2021 Reg. Sess. Section 3 (Md. 2021) (enacted).

[3] Id. Sec. 1 §§ (a)(3)(vi)(1), (a)(3)(vi)(2).

[4] Id. Sec. 1 § (a)(3)(vi)(3).

[5] S.B. 4, 2021 Reg. Sess. (Ky. 2021) (enacted).

[6] Va. Code § 19.2-56(B) (“No law-enforcement officer shall seek, execute, or participate in the execution of a no-knock search warrant.”) (as amended by legislation approved by governor on October 28, 2020).

[7] See, e.g., S.B. S8527, 2019-2020 Leg. Sess. (N.Y. 2020); 2021 Assemb. B. 137, 2021-2022 Leg. (Wis. 2021); Letter from Dave Yost, Attorney General, Ohio, to Mike DeWine, Governor, Ohio et al. (Oct. 15, 2020),

[8] Alisha Haridasani Gupta and Christine Hauser, New Breonna Taylor Law Will Ban No-Knock Warrants in Louisville, Ky., N.Y. Times (June 12, 2020),

[9] Oregon v. Arce, 730 P.2d 1260, 1262, 83 Or. App. 185 (Or. Ct. App. 1986); see Or. Rev. Stat. § 133.575(2) (“The executing officer shall, before entering the premises, give appropriate notice of the identity, authority and purpose of the officer to . . . the person in apparent control of the premises to be searched . . . .”); id. § 133.565 (containing no provision for authorizing no-knock entry).

[10] See Or. Rev. Stat. § 133.235(6) (permitting forceful entry to effect an arrest only “after giving notice of the officer’s identity, authority and purpose”); id. § 133.140(7) (“A warrant of arrest shall:  Specify that the arresting officer may enter premises, in which the officer has probable cause to believe the person to be arrested to be present, without giving notice of the officer’s authority and purpose, if the issuing judge has approved a request for such special authorization.”).

[11] Alaska Stat. § 12.25.100; Fla. Stat. §§ 901.19(1), 933.09

[12] See, e.g., Oregon v. Ford, 801 P.2d 754, 763, 310 Or. 623 (Or. 1990) (excusing compliance with the knock-and-announce requirement “if specific and articulable facts known at the time of entry . . . would lead a reasonable person to believe that compliance would create a risk to the entering officers’ safety”); Lockwood v. Alaska, 591 P.2d 969, 972 (Alaska 1979) (adopting an exception for “substantial compliance”); Trosper v. Alaska, 721 P.2d 134, 135 (Alaska Ct. App. 1986) (“Strict compliance with the knock and announce rule is not required when a balancing test indicates that the exigencies outweigh the hinderance to . . . respecting individuals’ privacy, and minimizing the destruction of property and the possibility of forcible resistance.”); Kellom v. Florida, 849 So.2d 391, 395 (Fla. Ct. App. 2003) (listing four exceptions to the knock-and-announce rule (citing Benefield v. Florida, 160 So.2d 706, 710 (Fla. 1964)).

[13] In 2005, the Maryland legislature authorized the issuance of no-knock warrants.  2005 Md. Laws Ch. 560.  In 2006, as discussed infra, the Supreme Court of the United States decided Hudson v. Michigan.

[14] Ford v. Maryland, 967 A.2d 210, 230-32, 184 Md. App. 535 (Md. Ct. Spec. App. 2009); Maryland v. Savage, 906 A.2d 1054, 1082-89, 170 Md. App. 149 (Md. Ct. Spec. App. 2006); see also Parker v. Maryland, 936 A.2d 862, 882, 402 Md. 372 (Md. 2007) (“Whether such an exclusionary rule should be applied when there are violations of the Maryland ‘knock and announce’ principle in other cases, or in cases arising after the effective date of Ch. 560 of the Acts of 2005, are matters which we leave for another day.”)

[15] See, e.g., Ohio v. Bembry, 90 N.E.3d 891, 151 Ohio St. 3d 502 (Ohio 2017).

[16] New Mexico v. Jean-Paul, 295 P.3d 1072, 1076-77, 2013-NMCA-032 (N.M. Ct. App. 2013) (citing New Mexico v. Attaway, 870 P.2d 103, 112 n.6, 117 N.M. 141 (N.M. 1994)); Pennsylvania v. Frederick, 125 A.3d 748, 77, 2015 PA Super 206 (Pa. Super. Ct. 2015) (citing Pennsylvania Supreme Court authority).

[17] Lum v. Koles, 314 P.3d 546, 557 (Alaska 2013) (citing Berumen v. Alaska, 182 P.3d 635, 642 (Alaska Ct. App. 2008)); Florida v. Cable, 51 So.3d 434 (Fla. 2010).

[18] Va. Code § 19.2-56(B) (“Any evidence obtained from a search warrant executed in violation of this subsection shall not be admitted into evidence for the Commonwealth in any prosecution.”).

[19] Lustig v. United States, 338 U.S. 74, 79 (1949).

[20] 364 U.S. 206 (1960).

[21] Constitutional Law-Search and Seizure-No Knock Entry Held Reasonable in Virginia When Exigencies Present, 7 U. Rich. L. Rev. 565, 565 (1973); see, e.g., Miller v. United States, 357 U.S. 301 (1958).

[22] See, e.g., Comment, “No Knock” Search and Seizure and the District of Columbia Crime Act:  A Constitutional Analysis, 62 J. Crim. L., Criminology & Police Sci. 350, 351 (1971) (“The ‘no knock’ search and seizure provision will likely be construed to be constitutional under the fourth amendment, with a properly narrow interpretation.”); Michael B. Sonnenreich & Stanley Ebner, No-Knock and Nonsense, An Alleged Constitutional Problem, 44 St. John’s L. Rev. 626 (1970) (arguing for a less strict understanding of the constitutional restrictions on no-knock arrests).

[23] Wilson v. Arkansas, 514 U.S. 927, 934 (1995).

[24] Id. at 934-46.

[25] Richards v. Wisconsin, 520 U.S. 385 (1997).

[26] Id. at 394.

[27] Id. at 394-95.

[28] 547 U.S. 586 (2006).

[29] Id. at 592.

[30] Id. at 593-94.

[31] Id. at 595-99.

[32] But see United States v. Weaver, 808 F.3d 26, 37-38, 42-25 (D.C. Cir. 2015) (limiting Hudson to search warrants and excluding evidence obtained during unannounced execution of an arrest warrant).

[33] Weaver, 808 F.3d at 42-45.

[34] Ker v. California, 374 U.S. 23, 37 (1963) (Clark, J., plurality opinion) (citing Supreme Court authority) (“It is contended that the lawfulness of the petitioners arrests, even if they were based upon probable cause, was vitiated by the method of entry.  This Court, in cases under the Fourth Amendment, [h]as long recognized that the lawfulness of arrests for federal offenses is to be determined by reference to state law insofar as it is not violative of the Federal Constitution.”); see also Virginia v. Moore, 553 U.S. 164, 172-73 (2008) (citing Supreme Court authority).

[35] See Moore, 553 U.S. at 171-72 (stating that the Supreme Court has, under its supervisory power, excluded evidence obtained through violations of state law but that admission of such evidence would not violate the Fourth Amendment).

[36] Fed. R. Evid. 402.

[37] United States v. Clyburn, 24 F.3d 613, 616 (4th Cir. 1994).

[38] United States v. Seerden, 916 F.3d 360, 366 (4th Cir. 2019) (“[T]he Fourth Amendment provides the proper standard for determining whether evidence seized pursuant to a non-federal warrant is admissible in federal court.” (citing Id. at 616; United States v. Van Metre, 150 F.3d 339, 346-47 (4th Cir. 1998)).

[39] United States v. Clenney, 631 F.3d 658, 667 (4th Cir. 2011).

[40] 364 U.S. at 249-51 (Frankfurter, J., dissenting).

[41] U.S. Sentencing Comm’n, 2020 Annual Report and Sourcebook of Federal Sentencing Statistics 45-46, 198 (2021),

[42] Id. at 46.

[43] Pub. L. No. 91-513 §§ 100-709, 84 Stat. 1236, 1242-84 (1970).

[44] See 547 U.S. at 591-94.

[45] Id. at 596-97.

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