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Criminal procedure

DNA collection and analysis

DNA (deoxyribonucleic acid) is genetic material found in blood, hair, saliva, bone, tissue, and bodily fluids that identifies the specific person from whom it came, to the exclusion of all other persons on earth (except for identical twins, who share the same genetic code). DNA collection and analysis gives the criminal justice system a powerful tool for convicting the guilty and exonerating the innocent.
Only one-tenth of a single percent of DNA (about 3 million bases) differs from one person to the next. After extracting DNA from bodily materials, scientists record an individual’s variations at these bases to generate their DNA profile.

In criminal cases this generally involves obtaining samples from crime-scene evidence and a suspect; extracting the DNA; and analyzing the DNA to characterize the variations at a set of specific variable regions (markers). If the sample profiles don't match, the person did not contribute the DNA at the crime scene. If the patterns do match, the suspect may have contributed the evidence sample.

The United States Supreme Court has held that when the police make a valid arrest supported by probable cause, the accused's expectations of privacy are not violated by the minor intrusion of a brief swab inside of the accused’s mouth (cheeks) to extract a sample of DNA material. The Supreme Court reasoned that the context of arrest gives rise to significant state (government) interests in identifying the accused so that (1) the proper name can be attached to the charges and (2) the criminal justice system can make informed decisions concerning pretrial custody.

For these reasons, the Supreme Court concluded that DNA identification of persons arrested is a reasonable search that can be considered part of a routine booking procedure. When officers make an arrest supported by probable cause to hold the person for a serious criminal offense and bring the suspect to the police station to be detained in custody, taking and analyzing a cheek swab of the arrestee's DNA is like fingerprinting and photographing—a legitimate police booking procedure that is reasonable under the Fourth Amendment. See Maryland v. King, 133 S.Ct. 1958 (2013).

Approximately 30 states and the federal government have laws that authorize the collection and analysis of the DNA of persons arrested or charged with certain crimes—before such persons are convicted of any crimes. State laws allowing for the collection and analysis of DNA upon arrest are often based on the type of crime involved—with some states permitting it for all felonies; some states permitting it only for certain felonies; and some states permitting it for certain misdemeanors and felonies. And some states allow DNA collection and analysis of juveniles charged with qualifying criminal offenses.

These DNA collection and analysis laws are also known as DNA arrestee laws and are generally located in a state’s statutes.

In Texas, DNA collection and analysis are integral parts of the criminal justice system, used for identifying individuals involved in crimes. Texas law permits the collection of DNA samples from individuals arrested for certain crimes. The process involves obtaining DNA from a suspect or crime scene evidence, extracting and analyzing it to create a DNA profile, which can then be compared to determine a match. The U.S. Supreme Court, in Maryland v. King, has upheld the constitutionality of DNA collection upon arrest for serious offenses as part of routine booking procedures, akin to fingerprinting and photographing, under the Fourth Amendment. Texas aligns with this ruling and other states by allowing DNA collection upon arrest, primarily for felony offenses, and in some cases, for certain misdemeanors. The state statutes detail the specific circumstances under which DNA can be collected from arrestees and juveniles charged with qualifying offenses.

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