Arrest
Although a criminal case may begin in other ways, it most often begins with an arrest. Often it is obvious when an arrest has occurred, but sometimes it is not. There are no "magic words." A police officer need not say, "You are under arrest." An arrest has great legal significance. Police have obligations after an arrest, which they do not have before it. If police do not fulfill these obligations, a defendant may benefit and prosecutors may be denied the use of incriminating evidence. Thus, courts are often called upon to determine the exact point of arrest. The courts will consider the opinion of the arresting officer and of the arrested person, but these are not decisive. The courts will find an arrest has occurred at the moment a reasonable person (but not necessarily the officer or the defendant) would have believed he was no longer free to leave and go about his business. If you have been arrested, police must inform you of your right to remain silent. If you are silent after being arrested, your silence cannot be used against you. But the right to remain silent is not so absolute before an arrest, and police do not need to inform you about it at all. If a court later rules that you were not under arrest at the time, it is possible that prosecutors might attempt to use your mere silence against you. To protect against that possibility, it might be useful to repond to police questions by saying something like, "On the advice of counsel, I do not wish to say anything."
Police officers have legitimate authority to arrest only in certain circumstances. An officer has a lawful "power of arrest" when he has reasonable grounds to believe a suspect has committed a felony (any crime punishable by a state prison sentence), or reasonable grounds to believe the suspect has committed certain misdemeanors (crimes punishable only by county jail sentence or fine) when such power of arrest is particulary granted by statute (operating under the influence is one example). An officer may lawfully arrest for other misdemeanors only if the crime is committed in his presence and that misdemeanor amounts to a breach of the peace. If a court later finds the officer did not have a legitimate power of arrest, the arrest will be held to be unlawful. A defendant would ordinarily reap some benefit from such a holding, possibly the suppression of evidence, possibly even dismissal of the charges.
Since colonial days, the citizens of Massachusetts have had the legal right to resist an unlawful arrest by using reasonable force. But in 1983, the Supreme Judicial Court held that the reasons which led to the recognition of such a right were no longer valid. See Comm v. Moreira, 388 Mass. 596 (1983). Consequently, our law now requires a person to submit even to an unlawful arrest by a police officer. However a person being arrested, whether lawfully or unlawfully, may use reasonable force to defend himself against the use of excessive or unnecessary force by police. This may be imprudent or even dangerous, but it is legally permissible. Also, this defense would be forfeit if an arrestee continues to use force after it has become apparent that if he ceased resisting by force the officer would cease using excessive force (how this would ever become "apparent" is not at all clear). All such questions might later have to be determined by a jury or a judge.