In the case of Crystal M. Ferguson, et al. v. City of Charleston et al., 2000, the U.S Supreme Court ruled that a state hospital's performance of a diagnostic test to obtain evidence of drug use for law enforcement purposes constitutes an unreasonable search if the patient has not consented to it. The case involved pregnant women who were tested for cocaine usage without their knowledge or consent at a public hospital in Charleston, South Carolina; positive results were reported to police under a policy developed by city officials and medical personnel from the Medical University of South Carolina (MUSC). The court held that this violated Fourth Amendment rights against unreasonable searches and seizures because patients did not provide informed consent and there was no immediate threat to life or limb requiring such tests without warrant or individualized suspicion.

In the dissenting opinion for Crystal M. Ferguson, et al. v. City of Charleston et al., Chief Justice Rehnquist, joined by Justices Scalia and Thomas, argued that the hospital's drug testing policy was not intended to be used in a prosecutorial capacity but rather as a means to protect both mothers and their unborn children from potential harm caused by drug use during pregnancy. The dissenters believed that this protective intent should exempt it from needing individualized suspicion before conducting such tests under the Fourth Amendment’s special needs doctrine. They also pointed out that patients were informed about this policy upon admission and could have chosen another hospital if they disagreed with it; thus implying consent on part of those tested positive for cocaine use.