An arrestee who lies to a booking officer about possessing a weapon voluntarily enters the jail for purposes of violation of Penal Code section 4574. Ross was arrested for assault with a knife. Police did not find a knife during a patdown search. Upon arriving at the jail, Ross denied having any weapons in her possession. During a booking search, another officer found a knife in Ross’s undergarments. The trial court set aside the information which alleged that Ross brought a weapon into the jail in violation of Penal Code section 4574, because she had not voluntarily brought the weapon into the jail. The prosecutor appealed, and the appellate court reversed the order. The plain language of the statute penalizes knowingly carrying a weapon into the jail. Where the arrestee lies to the booking officer by denying possession of a weapon and then enters the jail, the arrestee has violated section 4574 by voluntarily choosing to enter the jail with the weapon.