It happens frequently. A police officer stops an individual on the street and asks for identification. The person -- a criminal who wants to hide his real identity -- provides false identification. The officer calls in the name and the computer check turns up nothing. The person is released by the officer and the police miss an opportunity to nab a bad guy.

The Federal Bureau of Investigation (FBI) has come up with what it believes to be a solution to the problem of identifying individuals

in these circumstances. Put a mobile fingerprint matching device in a police cruiser and link it via radio transmission to the National Crime Information Center (NCIC) database. According to the FBI, such a system would provide police officers with accurate identification of individuals who are currently listed in the wanted, convicted, missing and unidentified person files.

Later this year, the FBI will test the concept in cruisers used by the Alexandria, Va., Police Department. If all goes well, the service will be available to law enforcement agencies nationwide by late 1999 when the FBI finishes its massive upgrade of NCIC 2000. But mobile fingerprint matching faces several hurdles before it becomes another crime-fighting tool in the law enforcement arsenal.

Not IAFIS

The NCIC 2000 fingerprint-matching system would allow police to live-scan a single right index fingerprint from a squad car or a police booking station. The system captures the image, extracts the minutiae and other important data, and compresses the image. It then sends all the information to NCIC 2000 to determine if a match can be made.

One thing it won't do is pull up criminal history records. The FBI is quick to point out that this is not the same as the Integrated Automated Fingerprint Identification System (IAFIS), the bureau's sophisticated identification system, still under development, that relies on a massive database of fingerprint images and criminal history records. IAFIS will house digital images of the 10-print cards that law enforcement agencies submit to the FBI on a regular basis. Eventually, IAFIS will provide matching capabilities for as many as 36 million fingerprints.

In contrast, the goal of NCIC's mobile fingerprint matching is to provide quick responses to inquiries, searching a database of the 30,000 most dangerous criminals listed in the NCIC database, said Bill Casey, a deputy superintendent with the Boston Police Department.

Like today's NCIC fingerprint system, NCIC 2000 will use radio channels to transmit image data from the cruiser's mobile live-scan device to the network that connects to the NCIC database. In most jurisdictions, the mobile channels for police radios have a low capacity and must be shared by many users.

To achieve a quick response time, the NCIC fingerprint system will only capture the minimal data needed by the fingerprint matcher. The data will need to be compressed to speed transmission time. How the data will be compressed is another issue. According to the FBI, the NCIC system will not be able to use certain compression routines, such as WSQ (Wavelet Scalar Quantization) and JPEG (Joint Photographic Experts Group), because they are too large to send over a radio channel in a short period of time.

Even if the FBI is able to significantly compress the image data, it might not be enough, given the law enforcement community's growing demand for data transmissions, according to James Zepp, technical assistance director at the Justice Research and Statistics Association. "The radio frequencies that have been set aside for public safety transmissions are very limited in capacity because they were originally set up for short voice messages, not data transmission," he said.

Public safety agencies have asked the Federal Communications Commission to set aside more spectrum on the radio band so that data transmission by public safety agencies will be more practical. "The use of