Public officers invested with judicial powers for the purpose of preventing breaches of the peace, and bringing to punishment those who have violated the law. 2. These officers, under the Constitution of the United States and some of the states, are appointed by the executive in others, they are elected by the people, and commissioned by the executive. In some states they hold their office during good behaviour, in others for a limited period. 3. At common law, justices of the peace have a double power in relation to the arrest of wrong doers; when a felony or breach of the peace has been committed in their presence, they may personally arrest the offender, or command others to do so; and in order to prevent the riotous consequences of a tumultuous assembly, they may command others to arrest affrayers, when the affray has been committed in their presence. If a magistrate be not present when a crime is committed, before he can take a step to arrest the offender, an oath or affirmation must be made by some person cognizant of the fact that the offence has been committed, and that the person charged is the offender, or there is probable cause to believe that he has committed the offence. 4. The Constitution of the United States directs, that no warrants shall issue, but upon probable cause, supported by oath or affirmation. Amendm. IV. After his arrest, the person charged is brought before the justice of the peace, and after bearing he is discharged, held to bail to answer to the complaint, or, for want of bail, committed to prison. 5. In some, perhaps all the United States, justices of the peace have jurisdiction in civil cases, given to them by local regulations. In Pennsylvania, their jurisdiction in cases of contracts, express or implied, extends to one hundred dollars.