Preventive detention concerns imprisonment either without justification (the prisoner is not told the grounds for the arrest) or waiting for trial. In most democracies, no one can be arrested without being told the grounds for such an arrest, except under rare and special circumstances (usually anti-terrorism legislation). An arrested citizen has to be brought before the nearest magistrate within a certain amount of time. The arrested person has the right to defend himself by a lawyer of his choice. Depending on the laws, this lawyer can be called for as soon as the detention starts, or sometimes days or weeks later.