In the context of Terry v. Ohio, what is required for a stop and frisk to be justified?

In the context of Terry v. Ohio, the key requirement for a stop and frisk to be justified is "reasonable suspicion of dangerous criminal activity." This landmark Supreme Court decision established that law enforcement officers do not need probable cause to conduct a brief stop and pat-down of an individual; instead, they must have a reasonable belief that the person is involved in criminal activity and may be armed and dangerous.

Reasonable suspicion is based on the officer's observations, experience, and specific facts that can lead to a belief that a suspect may be involved in crime. This standard is less stringent than the probable cause standard required for arrests or search warrants, allowing police to respond to potential threats and protect themselves and the public from harm.

The other options involve higher thresholds of evidence that are not necessary for a stop and frisk. Probable cause, for instance, is a requirement for arrests and obtaining search warrants, while substantial evidence of wrongdoing implies a greater level of proof that exceeds the reasonable suspicion standard. A formal arrest entails taking someone into custody, which is not a prerequisite for the stop-and-frisk procedure established in this case.