The availability of a communication channel that could be everywhere accessible, possibly via wireless devices is a constant matter for the police force. The well-developed public cellular network infrastructure and widespread mobile device can provide with such features, but the lack of security makes it unsuitable for transmitting confidential data. In this paper, we propose a security framework for mobile police information system to transmit sensitive information confidentially over the public cellular network, and describe the authentication and communication protocol in detail. The test on a physical GSM based cellular network reveals that it is suitable for actual needs both in speed and security.