WHEN IS A PERSON "UNDER ARREST"?
Many people think of an arrest as being a formal statement by the police, "You are under arrest," followed by the reading of the "Miranda rights". (Like on TV: "You have the right to remain silent. Anything you say can and will be used against you in a court of law. You have the right to an attorney. If you cannot afford an attorney, one will be appointed to represent you.")
Reality is a little bit more complicated. An arrest occurs when a person no longer reasonably expects that he is free to leave. You should be aware that there is a big, legal difference between a "detention" and an arrest. A "detention" occurs when a police officer stops someone because they have an "articulable" or definable suspicion that a crime has occurred. The person can't leave when he's detained, but the detention must be of a short duration and is limited in its scope. A typical detention occurs where someone is stopped for a traffic violation. The officer may ask a few questions to identify the person and his passengers and can hold them there to find out if there really is a violation. But he can't stop someone as an excuse to search the car or the people inside.
But, if a person is not allowed to leave the scene for an extended period of time, the person may be considered to be "under arrest," even though the "magic" words are never used. If a person is handcuffed, is locked in the back of a police car, or is otherwise kept from leaving (seated on the curb while handcuffed, or surrounded by police), the person will ordinarily be considered to be "under arrest."
WHAT IF THE POLICE WANT TO SEARCH ME OR MY PROPERTY?
You can refuse the police permission to conduct a search. Remember that the police officer wants to search for evidence of criminal activity, and the fact that he is asking means that he thinks he will find some. You are entitled to say "No." If the police officer has the legal authority to perform the search (a printed search warrant signed by a judge), he will do so whether or not you agree. However, if he does not have the legal authority to perform a search and you agree to let him search, you cannot complain about it later, because you have given him the right.
The same applies for a traffic stop. Many times the officer will try to get your permission to search. He has nothing to lose by asking. Often he asks in a way that makes it seem like you don't have any choice. But you do. If you give the police officer permission, he can perform the search even if he otherwise had no legal authority to do so. Most people don't want the police to think they have something to hide, even if they really do! The lesson is: Don't say yes. Say "no". Deny permission. Even if he goes ahead, you may claim lack of consent later.
DO THE POLICE HAVE TO "READ ME MY RIGHTS" WHEN I AM ARRESTED?
The police have no duty to formally announce the arrest when it occurs, or to read a suspect his "Miranda" rights. Typically, at some point the police will inform a suspect that he has been arrested. However, many defendants never receive their "Miranda Rights". These rights only need to be disclosed when the police want to question someone who is already under arrest, either at the side of the road, in the police car, or at the station or jail.
CAN I BE ARRESTED WITHOUT A WARRANT?
For most misdemeanor offenses, a police officer can only make a warrantless arrest of a suspect if the offense was committed in the officer's presence. Officers can arrest people for felonies based upon witness statements, or where a warrant for the person's arrest has been issued.
IF I AM ARRESTED, CAN THE POLICE SEARCH ME?
The police have the authority to perform a search of a suspect and his immediate surroundings, "incident" to the arrest of the suspect. If the police arrest a person who was driving a car, they ordinarily get the authority to search the entire passenger compartment of the car - and will usually also be able to search passengers for weapons. If the car is impounded, the police may perform an "inventory search" of the entire car, including the contents of the trunk.