In criminal law, a suspect is someone who is under suspicion, often formally announced as being under investigation by law enforcement officials. Probable cause for an arrest exists when the facts and circumstances within the arresting officer's knowledge are sufficient to warrant a prudent person to believe that a suspect has committed, is committing, or is about to commit a crime.
Once a person is determined to be a prime suspect (the person believed most likely to have committed the crime), the police must be careful to give the "Miranda warnings," or or else any statements or admissions by the suspect may be excluded from evidence in trial. Once a suspect under arrest tell a law enforcement officer that he wants an attorney, all interrogation must cease, subject to certain exceptions.
