The U.S. Supreme Court case ONE 1958 PLYMOUTH SEDAN v. PENNSYLVANIA, decided in 1964, revolved around the Fourth Amendment's protection against unreasonable searches and seizures. The state of Pennsylvania had seized a Plymouth Sedan under a state law that allowed for the confiscation of vehicles used to transport illegal alcohol without needing to provide any compensation to the owner. However, this seizure was based on evidence obtained through an unlawful search by police officers who did not have a warrant or probable cause at the time of their search. The Supreme Court ruled in favor of the vehicle's owner, stating that it was unconstitutional for states to use illegally obtained evidence as justification for seizing property because it violated Fourth Amendment rights.

In the dissenting opinion for ONE 1958 PLYMOUTH SEDAN v. PENNSYLVANIA, Justice Harlan argued that the majority's decision to apply exclusionary rules to forfeiture proceedings was a significant and unnecessary expansion of Mapp v. Ohio (1961). He contended that this extension would have far-reaching implications beyond just automobile forfeitures, potentially affecting all civil in rem proceedings where property is seized due to its involvement in criminal activity. Furthermore, he pointed out that such an application could lead to absurd results; for instance, if contraband were discovered during an illegal search and seizure operation but later independently found through legal means, it could still be subject to return under the majority's ruling. This outcome would undermine law enforcement efforts while providing no additional protection of constitutional rights since any evidence obtained illegally is already excluded from criminal trials.