If you believe you have PC for an arrest but the judge disagrees, you've made an unconstitutional arrest. If the judge finds your reasons for making a detention don't add up to reasonable suspicion, you've made an unconstitutional detention. But because consensual encounters do not require any showing of suspicion whatsoever, there's no opportunity for a court to find that you've made an unconstitutional consensual encounter. For Fourth Amendment purposes, the consensual encounter is risk-free; a detention is not. Therefore, which of these choices should be your preferred method of attempting contact with a suspect?
Distinguishing a Consensual Encounter From a Detention
The essential test of a detention is to look at all of the surrounding circumstances and ask whether, in view of what officers have said and done, a reasonable, innocent person in this situation would have felt that he no longer had a choice about coming or going as he pleased, but was compelled by official authority to submit to the interaction with police.
What kinds of actions could convert a consensual encounter into a detention, requiring reasonable suspicion? "Examples of circumstances that might indicate a seizure, even where the person did not attempt to leave, would be the threatening presence of several officers, the display of a weapon by an officer, some physical touching of the person, or the use of language or tone of voice indicating that compliance with the officer's request might be compelled." (U.S. v. Mendenhall) In a series of cases, the Supreme Court has expressed the distinction as follows:
"A person has been 'seized' only when, by means of physical force or a show of authority, his freedom of movement is restrained. As long as the person to whom questions are put remains free to disregard the questions and walk away, there has been no intrusion on that person's liberty or privacy as would under the Constitution require some particularized and objective justification." (U.S. v. Mendenhall)