Master The Supreme Court held that police may, without a warrant, take and analyze a buccal swab of an arrestee’s DNA for serious offenses as part of routine booking, consistent with the Fourth Amendment. with this comprehensive case brief.
Maryland v. King is a landmark Fourth Amendment decision addressing whether law enforcement may collect a cheek swab of DNA from individuals arrested for serious offenses without a warrant and use it to check for matches in a national database. The Supreme Court framed the practice as a legitimate part of the routine booking process—akin to fingerprinting and photographing—used to identify arrestees and inform custodial decisions, rather than as an investigative technique aimed solely at solving unrelated crimes. By applying the Fourth Amendment’s general “reasonableness” balancing test, the Court upheld Maryland’s statute authorizing such DNA collection.
The case is significant because it broadened the scope of permissible suspicionless searches incident to arrest by endorsing DNA collection at booking for serious crimes. It intensified debates over the boundary between identification and investigation, the privacy implications of biometric technologies, and the potential for database-driven policing to erode traditional limits on searches. The decision has shaped statutes, police practices, and later doctrinal discussions about biometric data and digital privacy.
Maryland v. King, 569 U.S. 435 (2013)
In 2009, Alonzo King was arrested in Maryland for first- and second-degree assault. During booking, police collected a buccal (cheek) swab of his DNA pursuant to Maryland’s DNA Collection Act, which authorized DNA sampling from individuals arrested for crimes of violence or burglary. Under the statute, the DNA sample could not be processed until after a judicial determination of probable cause, and it was to be destroyed if the charges were not sustained or if the arrestee was acquitted. After processing, King’s DNA profile was uploaded to CODIS, the national DNA database, and it matched an unsolved 2003 rape. Based on the match, prosecutors charged King with the rape and introduced the DNA evidence at trial. King moved to suppress, arguing that the DNA collection and analysis violated the Fourth Amendment. The trial court denied the motion, and King was convicted of the rape. The Maryland Court of Appeals reversed, holding the Act unconstitutional as applied to arrestees. The U.S. Supreme Court granted certiorari and reversed the Maryland high court.
Does the Fourth Amendment permit police, without a warrant and without individualized suspicion, to take and analyze a buccal swab of DNA from an individual arrested for a serious offense as part of the routine booking process?
Under the Fourth Amendment, the reasonableness of a search is assessed by balancing the degree of intrusion on an individual’s privacy against the degree to which the search advances legitimate governmental interests. Warrantless, suspicionless searches may be reasonable when conducted as part of routine booking procedures for arrestees with diminished expectations of privacy, particularly when the search is minimally intrusive and serves important governmental interests in identification and safe, informed custodial decisions. A buccal swab taken from an arrestee for a serious offense, analyzed for limited identifying markers and subject to statutory protections, is constitutionally reasonable as part of the booking process.
Yes. Taking and analyzing a cheek swab of DNA from an arrestee for a serious offense is, like fingerprinting and photographing, a legitimate booking procedure that is reasonable under the Fourth Amendment. The Supreme Court reversed the judgment of the Maryland Court of Appeals.
The Court, applying the general reasonableness balancing test, emphasized that arrestees have a diminished expectation of privacy due to a lawful custodial arrest based on probable cause. The physical intrusion of a buccal swab is minimal, brief, and painless; it resembles traditional identification procedures such as fingerprinting and photographing. Maryland’s statute further reduced privacy concerns by limiting analysis to specific non-coding loci used for identification (the CODIS markers), delaying analysis until after a judicial determination of probable cause, and providing for expungement of the sample/profile if charges did not result in conviction. On the government’s side of the balance, the Court credited several weighty interests: accurately identifying the person in custody; uncovering criminal history to inform bail, pretrial release, and custodial placement decisions; ensuring officer and detainee safety; and connecting the person to past crimes when relevant to those decisions. The Court analogized DNA profiling to fingerprinting, concluding that both are primarily identification tools that also can reveal outstanding warrants or connections to other crimes. The majority rejected the contention that DNA swabbing is an impermissible general crime-control measure. It characterized the purpose of the swab as identification, not evidence-gathering for unrelated investigations, noting statutory limits on use, the narrow set of markers analyzed, and the timing (post–probable cause determination) as safeguards against abuse. It also emphasized that the holding was confined to arrestees for serious offenses. In dissent, Justice Scalia, joined by three Justices, argued that the program’s true aim was to solve cold cases, not to identify arrestees, as evidenced by the delay between collection and results and the sufficiency of conventional identification methods. He warned that allowing suspicionless DNA collection for ordinary law enforcement objectives erodes the warrant requirement and risks normalizing universal DNA sampling. The majority, however, found the balance tipped decisively in favor of reasonableness under the Fourth Amendment.
Maryland v. King validates DNA cheek swabs of arrestees for serious offenses as part of routine booking, expanding the scope of permissible suspicionless searches under the Fourth Amendment. It cements a doctrinal analogy between DNA profiling and fingerprinting, grounding reasonableness in a balancing approach rather than a warrant requirement or a narrow “special needs” framework. For law students, the case illustrates modern Fourth Amendment methodology, the interplay between technological change and privacy expectations, and how statutory safeguards can influence constitutional analysis. It also highlights fault lines between the majority’s identification rationale and the dissent’s crime-control critique—fault lines relevant to emerging debates over biometrics, database searches, and digital privacy.
No. The holding is framed around “serious offenses,” and Maryland’s statute limited collection to arrests for crimes of violence and burglary. While some jurisdictions have broader laws, King’s reasoning emphasizes the seriousness of the offense as a factor that helps make the search reasonable. Collecting DNA for minor offenses remains more constitutionally sensitive and may be vulnerable to challenge.
No. The Court held that a warrant is not required because the search is justified as a reasonable booking procedure incident to a lawful custodial arrest for a serious offense. The reasonableness is assessed by balancing privacy intrusions against governmental interests in identification and safe, informed custody.
The Court emphasized that both fingerprinting and DNA profiling serve core identification functions: confirming who is in custody, revealing criminal history, and flagging connections to outstanding warrants or offenses. The physical intrusion of a cheek swab is minimal, and statutory limits constrain analysis to non-coding loci used for identification, which the majority found comparable to traditional biometric techniques.
The dissent argued that the program’s true purpose was general crime control—solving unrelated crimes—rather than identification, making it a suspicionless, warrantless search for ordinary law-enforcement objectives. It warned that the reasoning could justify DNA collection from anyone arrested—even for minor offenses—and that delays between collection and results undercut the identification rationale. It also highlighted the privacy stakes of biological samples.
Under Maryland’s statute, analysis could not occur until after a judicial probable-cause determination, and the sample/profile had to be destroyed if charges were not sustained or if the individual was acquitted. Other jurisdictions have similar expungement provisions, though procedures and compliance vary and can be the subject of further litigation.
Maryland v. King marks a pivotal point in Fourth Amendment law by endorsing DNA cheek swabs as part of routine booking for serious offenses. By applying a balancing test and analogizing DNA to fingerprinting, the Court validated suspicionless DNA collection without a warrant where statutory safeguards limit use and analysis, emphasizing governmental interests in accurate identification and safe custodial decisions.
At the same time, the case underscores ongoing tensions between evolving identification technologies and privacy. The dissent’s warnings about mission creep and the potential normalization of broader DNA collection remain salient, inviting careful statutory design and vigilant judicial review as biometric technologies and databases continue to expand.