In which situation can a citizen legally perform an arrest under South Dakota law?

A citizen can legally perform an arrest under South Dakota law when they witness a crime being committed. This is a fundamental aspect of citizens' arrest laws, which allow individuals to take immediate action when they have direct knowledge of a crime taking place. Witnessing a crime provides the necessary grounds for an arrest since the citizen has firsthand observation of the illegal act.

In contrast, other scenarios, such as believing someone is about to commit a crime or simply acting suspiciously, do not provide the sufficient legal grounds for a citizen's arrest. These situations might warrant contacting law enforcement but do not justify taking physical action against an individual. Hearing about a crime on the news also does not establish direct knowledge or evidence of a crime occurring in real time, which is essential for legally effecting an arrest.