Final answer:
A police officer needs reasonable suspicion to conduct a Terry Stop, which is a lower legal threshold than probable cause and is based on the Supreme Court ruling in Terry v. Ohio.
Step-by-step explanation:
In order for a police officer to conduct a Terry Stop, the legal threshold that must exist is a. Reasonable suspicion. This is established by the case Terry v. Ohio, where the Supreme Court ruled that police may stop a person if they have reasonable suspicion that the person has committed or is about to commit a crime.
Furthermore, they may frisk the suspect for weapons if there is reasonable suspicion that the suspect is armed and dangerous. This standard is a lower threshold than probable cause, which is required for arrest warrants or most searches without a warrant.