In recent years, state and federal laws have facilitated law enforcement's expanded use of deoxyribonucleic acid (DNA) for investigating and prosecuting crimes. Such laws authorize compulsory collection of biological matter, which local law enforcement agencies send to the Federal Bureau of Investigation (FBI) for analysis. The FBI then stores unique DNA profiles in a national distributive database, through which law enforcement officials match individuals to crime scene evidence. Early laws authorized compulsory extraction of DNA only from people convicted for violent or sex-based felonies, such as murder, kidnapping, and offenses "related to sexual abuse"—crimes associated with historically high recidivism rates and for which police were likely to find evidence at crime scenes. Since the turn of the century, new laws have greatly extended the scope of compulsory DNA collection, both by expanding the range of offenses triggering collection authority, and, more recently, by authorizing compulsory collection from people who have been arrested but not convicted. A bill passed by the House in May 2010, the Katie Sepich Enhanced DNA Collection Act of 2010 ( H.R. 4614 ), would provide grant funding incentives to states that collected DNA samples from persons who are at least 18 years old who are arrested for specified types of crimes. Litigants have challenged compulsory collection and the subsequent analysis and storage of DNA as unreasonable searches and seizures under the Fourth Amendment to the U.S. Constitution. Although they have reached their conclusions using different analytical approaches, federal and state courts have generally upheld compulsory DNA collection as non-violative of the Fourth Amendment. However, prior cases involved the collection of DNA samples from people who had been convicted of a crime. More recently, a handful of state and federal courts have addressed such collection from arrestees, with differing results. This report examines statutory authorities, constitutional principles, and case law related to compulsory DNA extraction and analyzes potential impacts of recent developments for Fourth Amendment cases. DNA is a complex molecule found in human cells and "composed of two nucleotide strands," which "are arranged differently for every individual except for identical twins." Relatively new technology enables DNA analysts to determine the arrangement of these strands, thereby creating unique DNA profiles. In the law enforcement context, DNA profiles function like "genetic fingerprints" that aid in matching perpetrators to their crimes. As with fingerprints, law enforcement officers collect DNA samples from specific classes of individuals, such as prisoners. However, compulsory DNA collection generally entails blood or saliva samples rather than finger impressions, and DNA profiles can later match any of many types of biological matter obtained from crime scenes. For these reasons, DNA matching is considered a "critical complement to," rather than merely a supplement for, fingerprint analysis in identifying criminal suspects. The FBI administers DNA storage and analysis for law enforcement agencies across the country. Typically, a law enforcement agency's phlebotomist collects a blood sample pursuant to state or federal law. Then, the agency submits the sample to the FBI, which creates a DNA profile and stores the profile in the Combined DNA Index System, a database through which law enforcement officers match suspects to DNA profiles at the local, state, and national levels. FBI analysts create DNA profiles by "decoding sequences of 'junk DNA.'" So-called "junk DNA," the name for "non-genic stretches of DNA not presently recognized as being responsible for trait coding," is "'purposefully selected'" for DNA analysis because it is not "associated with any known physical or medical characteristics," and thus theoretically poses only a minimal invasion of privacy. The categories of individuals from whom law enforcement officials may require DNA samples has expanded in recent years. The federal government and most states authorize compulsory collection of DNA samples from individuals convicted for specified criminal offenses, including all felonies in most jurisdictions and extending to misdemeanors, such as failure to register as a sex offender or crimes for which a sentence greater than six months applies, in some jurisdictions. In addition, the federal government and some states now authorize compulsory collection from people whom the government has arrested or detained but not convicted. As discussed infra , the DNA Analysis Backlog Elimination Act 2000, as amended, authorizes compulsory collection from individuals in federal custody, including those detained, arrested, or facing charges, and from individuals on release, parole, or probation in the federal criminal justice system. Under the federal law, if an individual refuses to cooperate, relevant officials "may use or authorize the use of such means as are reasonably necessary to detain, restrain, and collect a DNA sample." State laws vary, but nearly all states authorize compulsory DNA collection from people convicted for specified crimes, and a small but growing number of states also authorize compulsory collection from arrestees. At the federal level, statutory authority for compulsory DNA collection has expanded relatively rapidly. During the 1990s, a trio of federal laws created the logistical framework for DNA collection, storage, and analysis. The DNA Identification Act of 1994 provided funding to law enforcement agencies for DNA collection and created the FBI's Combined DNA Index System to facilitate the sharing of DNA information among law enforcement agencies. Next, the Antiterrorism and Effective Death Penalty Act of 1996 authorized grants to states for developing and upgrading DNA collection procedures, and the Crime Identification Technology Act of 1998 authorized additional funding for DNA analysis programs. The resulting framework centers on the Combined DNA Index System; more than 170 law enforcement agencies throughout the country participate in the system. In recent years, federal and state laws have expanded law enforcement authority for collecting DNA in at least two ways. First, laws have increased the range of offenses which trigger authority for collecting and analyzing DNA. In the federal context, the DNA Analysis Backlog Elimination Act of 2000 limited compulsory extraction of DNA to people who had been convicted of a "qualifying federal offense." Under the original act, "qualifying federal offenses" included limited but selected felonies, such as murder, kidnapping, and sexual exploitation. After September 11, 2001, the USA PATRIOT Act expanded the "qualifying federal offense" definition to include terrorism-related crimes. In 2004, the Justice for All Act further extended the definition to reach all crimes of violence, all sexual abuse crimes, and all felonies. Similarly, almost all states now authorize collection of DNA from people convicted of any felony. Second, laws have authorized compulsory DNA collection from people who have been detained or arrested but not convicted on criminal charges. The 109 th Congress authorized the Attorney General, in his discretion, to require collection from such individuals. Specifically, the DNA Fingerprinting Act of 2005 authorized collection "from individuals who are arrested or from non-U.S. persons who are detained under the authority of the United States." The Adam Walsh Child Protection and Safety Act of 2006 subsequently substituted "arrested, facing charges, or convicted" for the word "arrested" in that authority. The U.S. Department of Justice implemented the authorization in a final rule that took effect January 9, 2009. Mirroring the statutory language, it requires U.S. agencies to collect DNA samples from "individuals who are arrested, facing charges, or convicted, and from non-United States persons who are detained under authority of the United States." As mentioned, some states have likewise enacted laws authorizing collection of arrestees' DNA. As mentioned, H.R. 4614 , a bill passed by the House, would provide grant funding incentives to encourage states to establish processes for collecting DNA from persons arrested for specified state offenses. Whereas the increase in the range of triggering offenses appears to be a natural outcome of DNA's success as a forensic tool, the expansion to collection from arrestees appears to be a more legally significant step. Overall, it seems Congress's goal for the expansion to arrestees and those facing charges was to facilitate crime prevention through "the creation of a comprehensive, robust database that will make it possible to catch serial rapists and murderers before they commit more crimes." In background material for its implementing rule, the Justice Department explains that collection from arrestees will facilitate more effective law enforcement for at least two reasons: (1) it will aid in crime prevention by ensuring that the government need not wait until a crime has been committed before creating an individual's DNA profile; and (2) it will allow federal authorities to create DNA profiles for aliens detained in the United States, who might not otherwise undergo judicial proceedings in U.S. courts. Although Congress expanded statutory authority for DNA collection, it has also provided some protection for arrestees whose arrests do not result in conviction. In particular, federal law mandates expungement of DNA samples upon an arrestee's showing of discharge or acquittal. The FBI and relevant state agencies "shall promptly expunge" DNA information "from the index" upon receipt of "a final court order establishing that such charge has been dismissed or has resulted in an acquittal or that no charge was filed within the applicable time period." Officials must also expunge DNA data for convicts in cases where a conviction is overturned. These provisions apply to DNA collected by state and local law enforcement officers, in addition to DNA collected in the federal justice or detention systems. The Fourth Amendment to the U.S. Constitution provides a right "of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures." Two fundamental questions arise in every Fourth Amendment challenge. First, does the challenged action constitute a search or seizure by federal or local government and thus trigger the Fourth Amendment right? Second, if so, is the search or seizure "reasonable"? Different tests trigger the Fourth Amendment right depending on whether a litigant challenges government conduct as a seizure or as a search. Seizures involve interference with property rights; a seizure of property occurs when government action "meaningfully interferes" with possessory interests or freedom of movement. In contrast, searches interfere with personal privacy. Government action constitutes a search when it intrudes upon a person's "reasonable expectation of privacy."