Bodily Samples

Fundamentals of Procedural Law by Adam J. McKee

Bodily samples are materials collected from a person’s body. They include blood, saliva, hair, fingerprints, and DNA, among other things. When law enforcement collects these samples, they’re conducting a type of search. This search falls under the Fourth Amendment of the U.S. Constitution, which protects citizens from unreasonable searches and seizures (U.S. Const. amend. IV).

Bodily Samples and the Fourth Amendment

The Fourth Amendment requires any search, including the collection of bodily samples, to be reasonable. A search is generally considered reasonable if it’s based on probable cause and a warrant is issued. Probable cause means there’s enough evidence to believe a crime has been committed.

However, exceptions to the warrant requirement exist. For instance, the Supreme Court has ruled that taking fingerprints without a warrant doesn’t violate the Fourth Amendment (Davis v. Mississippi, 394 U.S. 721, 1969).

DNA and the Fourth Amendment

DNA testing has become a vital tool in criminal investigations. However, collecting DNA samples often involves intimate personal procedures such as swabbing the inside of a person’s mouth.

In Maryland v. King (569 U.S. 435, 2013), the Supreme Court ruled that collecting DNA from arrestees for serious crimes is a legitimate police booking procedure akin to fingerprinting. The Court held that the benefits of DNA testing in solving crimes and identifying criminals outweigh the minimal intrusion into personal privacy.

Involuntary Blood Tests and the Fourth Amendment

In cases of drunk driving, law enforcement may wish to perform a blood test on a suspect. The Supreme Court has addressed this in Birchfield v. North Dakota (579 U.S. ___, 2016), stating that while breath tests may be performed without a warrant due to their minimal intrusion, blood tests are a different matter. A warrant is generally required for a blood test because it’s more invasive and implicates greater privacy concerns.


In criminal justice, bodily samples like blood, saliva, and DNA are types of searches. They’re governed by the Fourth Amendment, which mandates searches to be reasonable, typically needing probable cause and a warrant. However, some exceptions exist.

Fingerprints can be taken without a warrant, and DNA can be collected from arrestees of serious crimes due to its value in criminal investigations. For more intrusive samples, like blood tests, warrants are generally necessary. It’s essential to balance the needs of law enforcement with the privacy rights of individuals when considering these complex issues.

Modification History

File Created:  08/07/2018

Last Modified:  07/17/2023

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