In the 1993 case Terry Lee Shannon v. United States, the Supreme Court upheld a lower court's decision to convict and sentence Terry Lee Shannon for drug trafficking offenses. The main issue in this case was whether or not evidence obtained through a warrantless search of an automobile could be used against him in court. The defense argued that the police had violated his Fourth Amendment rights by conducting an illegal search without probable cause or consent, but the prosecution maintained that they were justified under what is known as "the automobile exception." This rule allows law enforcement officers to conduct searches if they have reasonable belief that contraband might be present within a vehicle due to its inherent mobility and reduced expectation of privacy compared with homes. In their ruling, the justices agreed with this argument and held that such searches do not violate constitutional protections against unreasonable seizures because vehicles can easily be moved out of local jurisdictions before warrants can be obtained.

In the dissenting opinion for Terry Lee Shannon v. United States, Justice Blackmun argued that the majority's decision to uphold Shannon's conviction under 18 U.S.C. § 922(g)(1) was incorrect because it failed to consider whether or not he knew of his status as a felon at the time of possession. He contended that knowledge is an essential element in proving a violation of this statute and without proof that Shannon knowingly possessed firearms while aware of his felony status, there could be no conviction. The majority’s interpretation, according to him, would lead to absurd results where individuals who unknowingly commit minor infractions could later face severe punishment if they possess firearms - even if they are unaware their past actions made them felons. This view contradicts traditional principles requiring mens rea (guilty mind) for criminal liability and thus should have been rejected by the court.