Final answer:
A person may arrest another when there are reasonable grounds to believe that the individual has committed a felony. This is related to the concepts of 'probable cause' and 'reasonable suspicion.' Arrests for misdemeanors without a warrant generally require the police to witness the crime.
Step-by-step explanation:
In legal terms, a person may arrest another when there are reasonable grounds to believe that a felony has been committed by the individual in question.
The concept of reasonable grounds is akin to probable cause, a legal standard that suggests a reasonable amount of suspicion, supported by circumstances sufficiently strong to justify a prudent and cautious person's belief that certain facts are probably true. The Fourth Amendment protects against unreasonable searches and seizures, requiring any warrant to be judicially sanctioned and supported by probable cause.
In the case of Terry v. Ohio, it was determined that police may stop a person if they have reasonable suspicion that the person is involved in criminal activity and may frisk the suspect for weapons if there is a reasonable suspicion that the person is armed and dangerous. However, the police's ability to arrest without a warrant for a misdemeanor is typically limited to instances where the misdemeanor was committed in their presence.