The federal system, the states and the District of Columbia each have their own criminal procedure codes - but every jurisdiction must comply with the U.S. Constitution.
The Constitution contains many provisions that protect individuals who have been arrested for or are merely suspected of a crime. Because of this requirement, criminal procedure is similar throughout the United States. Many states base their criminal procedure codes on the Federal Rules of Criminal Procedure.
The Police Must Have "Probable Cause" to Arrest You
Probable cause means there's enough evidence to indicate that you committed a crime - more likely than not. Mere suspicion is not enough to arrest you. The general rule is that the police must first obtain an arrest warrant from a judge after presenting evidence of probable cause at a hearing.
There are many exceptions to the warrant rule. The most notable exception is that a police officer can arrest you without a warrant if the officer actually sees you commit a crime.
You Cannot Be Searched Without Probable Cause
Before searching you, your car or your home, the police must have justification. Without probable cause, any evidence seized can be thrown out of court. The general requirement for a legal search is a search warrant. A search warrant is issued by a judge after law enforcement proves that a search is more likely than not to uncover evidence of a crime. As with arrest warrants, there are many exceptions to the search warrant rule. If a police officer knocks on your door and you invite the officer inside, for example, the officer can seize any evidence in plain view - without a search warrant.
If You Are Taken Into Custody, You Have Rights
You are "in custody" any time you are not free to leave - for example, if you are under arrest or if you've been taken to the police station for questioning. Before you can be questioned, a police officer must "read you your rights." These rights include the right to remain silent and the right to an attorney. If you say that you want to talk to an attorney, the police cannot question you until your attorney is present. You may request an attorney at any point during questioning. If the police violate either one of these rules, nothing you say can be used against you in court.
The Preliminary Hearing Determines Whether You'll Go to Trial
A preliminary hearing is held only if you plead not guilty. Some states will hold a preliminary hearing only if you are charged with a felony. Other states use grand juries instead of preliminary hearings. At the preliminary hearing, the prosecution presents evidence and makes arguments, and the defense makes arguments and attacks the prosecution's evidence. Weighing both sides, the judge decides whether or not there is probable cause to bring you to trial.
A Criminal Lawyer Can Help
The law surrounding criminal arrest and investigation is complicated. Plus, the facts of each case are unique. This article provides a brief, general introduction to the topic. For more detailed, specific information, please contact a criminal lawyer.