In the case of Pacileo, Sheriff v. Walker (1980), the U.S Supreme Court was asked to consider whether a state could constitutionally require an individual who has been arrested without a warrant to wait up to two days for a probable cause hearing. The petitioner, Sheriff Pacileo, argued that this delay did not violate the Fourth Amendment rights of the respondent, Walker. However, in its decision issued on November 12th 1980, the Supreme Court disagreed with this argument and ruled in favor of Walker. The court held that any significant delay between arrest and arraignment violated an individual's constitutional right against unreasonable seizures under Fourth Amendment protections if no judicial determination of probable cause is made promptly after arrest. This ruling effectively established that individuals arrested without warrants must be provided with prompt post-arrest hearings to determine if there is sufficient evidence or "probable cause" for their detention.

In the dissenting opinion for Pacileo, Sheriff v. Walker, it was argued that the majority's decision to grant habeas corpus relief based on a perceived violation of due process rights was incorrect. The dissenting justices believed that there had been no constitutional violation in this case as they felt that the defendant had not been denied his right to present a defense or confront witnesses against him. They also disagreed with the majority's interpretation of California law and its application in this case, arguing instead that state law did not require an instruction on lesser included offenses unless there was substantial evidence supporting such an instruction. Therefore, they concluded that since there wasn't any significant evidence suggesting guilt of a lesser offense rather than murder in this particular situation, failure by trial court to instruct jury about possible conviction for manslaughter didn’t violate petitioner’s federal constitutional rights.