Germany's High Court is banning police from installing spyware on computers of suspected criminals without their knowledge.

The decision is a blow to German Interior Minister Wolfgang Schäuble’s plans to give the Federal Criminal Police Office (BKA) greater power to monitor terrorists and criminals.

Two other judges had disagreed over whether police should be able to hack into suspected criminal’s computers and install spyware. In February, one judge approved police hacking but it was then barred by another, resulting in an appeal by federal prosecutors.

The High Court in Karlsruhe argued that searching computers is similar to searching homes and police should follow certain procedures, such as obtaining a search warrant and informing suspected offenders of a search.

The judges also argued that hacking computers by the police is not permitted under Germany's strict phone-tapping laws and that legislation would be needed to enable covert surveillance.

Last year, Schäuble persuaded the German Parliament to approve €132 million (US$171 million) for his Program for Strengthening Domestic Security which would allow the BKA to penetrate and to use the Internet to monitor PCs of suspected offenders in Germany.

The program also calls for greater use of video cameras in public places, biometric systems and other new security technologies.