Biometric face recognition as a police search tool - Foto-Fahndung

The "Foto-Fahndung" project confirmed that it is possible from a technical point of view to use face recognition systems in search scenarios. The tests were not confined exclusively to the algorithms of the manufacturers but encompassed complete systems to which the camera technology which was used in the monitoring of the area also belongs. If we take the complete systems into consideration, one system emerges a clear winner. This is system 2, which made the best overall impression. This system offered the best coordinated biometrics and camera technology package.

The field test showed that environmental conditions such as lighting and quick movements exert considerable influence on the recognition performances of the systems. Under real operational conditions, recognition performances of over 60% with a false acceptance rate of 0.1% can be achieved without any great time and effort being involved. By employing simple measures it should be possible to minimise the influences which still impacted negatively on the recognition performances in our field test. Through measures which steer the test persons' line of vision towards the cameras (e. g. a marquee in the proximity of the cameras), it would easily have been possible to again obtain better comparison images from the video stream. A higher number of frontal images would undoubtedly have brought about an increase in the number of correct matches and a decrease in the number of false acceptances.

If the possibility exists to split up the crowds and foster a co-operative form of behaviour, for example, during entry checks, it can be expected that the large majority of wanted persons will be reliably identified by a biometric face recognition system.

Depending on the operational situation, response times have to be planned for the operational forces who, in the case of an identification, will implement further measures. It has to be borne in mind that in a public place a person can already gain such distance from the surveillance area within one minute that it is difficult or impossible to find him again.

A realistically tolerable false acceptance rate of 0.1% is a manageable value. However, it also shows that the final decision on whether identification can be authenticated is always in the hands of a person who already adjudicates the on-screen identification. Otherwise, at Mainz central station about 23 citizens a day would have been subjected to further measures due to false acceptances.

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