What term describes a situation where no arrest warrant is needed when an officer arrests someone in the act of committing a crime?

The correct term that describes a situation where no arrest warrant is needed when an officer arrests someone in the act of committing a crime is "warrantless arrest." This concept is grounded in the legal principle that law enforcement officers have the authority to make an arrest when they directly observe someone committing a crime or when they have the immediate awareness that a crime is taking place. This allows officers to act swiftly to prevent further criminal activity, secure evidence, or prevent the suspect from fleeing.

When an officer witnesses a crime, they do not have to go through the lengthy process of obtaining a warrant, which can delay the response to the crime and potentially allow the suspect to escape or cause more harm. The ability to make warrantless arrests is crucial for effective law enforcement and is supported by various legal standards that prioritize public safety and the immediate apprehension of suspects during criminal acts.

In contrast, the terms associated with the other choices address different legal concepts. The "warrant requirement" refers to the necessity of obtaining a warrant in most circumstances before making an arrest, while "complaint application" pertains to the process of formally requesting an arrest warrant through a legal complaint. "Probable cause arrest" describes the standard of belief that is reasonable enough to cause a police