The violent criminal with multiple convictions – known by the inital M. – was sentenced to five years in prison back in 1986 before being taken into preventive detention. He has committed severe crimes, including several attempted murders. Preventive detention was limited to 10 years until German law was changed in 1998: unlimited custody of criminals became possible.

M., who now faces unlimited detention rather than the original 10-year period, complained that this practice constitutes unlawful retroactive implementation – an opinion which is also shared by the European Court of Human Rights. Hence, the allegedly dangerous criminal may be released from prison, though experts are convinced that he is a menace to society.

The courts in Marburg, Frankfurt and Karlsruhe found that keeping M. in the prison of Schwalmstadt would be lawful, but the ECHR in Strasbourg disagreed. The continuation of the preventive detention is in breach of the prohibition against double punishment, i.e. against human rights. That interpretation seems to be right.

Dozens of other prisoners like M. were also affected by the changed law in 1998: they also have to stay longer in prison, maybe for the rest of their lifetime. German courts regarded the continuation of preventive detention not as punishment, but the European Court did so. Should the decision in Strasbourg become res judicata,  about 500 convicted criminals may be released from prison – most of them are rapists and murderers.