Final answer:
Peace officers can arrest without a warrant if there is probable cause of a felony or witnessed misdemeanor. Searches and seizures typically require a warrant, with few exceptions. Illegally obtained evidence is barred from trial under the exclusionary rule.
Step-by-step explanation:
Under criminal procedure law, peace officers have the authority to make arrests without a warrant in specific situations where probable cause exists. Probable cause is a legal standard that requires a reasonable amount of suspicion, supported by circumstances sufficiently strong to justify a prudent person's belief that a person has committed, or is committing, a crime. For felony crimes, an officer may arrest without a warrant if there is probable cause to believe that the individual committed the offense. Similarly, officers can arrest an individual for a misdemeanor or minor crime if it is committed in their presence.
However, the Fourth Amendment of the U.S. Constitution prohibits unreasonable searches and seizures and mandates that a search or seizure must typically be carried out under the authority of a search warrant, issued upon probable cause. Exceptions to the warrant requirement include exigent circumstances, consent, and the plain view doctrine. Nonetheless, an illegal search or seizure can invoke the exclusionary rule, as confirmed by Mapp v. Ohio, which prohibits the use of evidence obtained in violation of the Fourth Amendment rights in a criminal trial.