The relationship between public authorities and private individuals raises difficult and controversial data protection issues. There is much anxiety on the part of civil rights campaigners about the seemingly incessant desire of the state to retain more and more information about its citizens, especially where the body holding the data is the police.

However, in an important decision, the Supreme Court has ruled that a police force did not break the law when it retained an elderly peace protestor's personal details on its database.

The 91-year-old man was associated with an anti-arms trade protest group, some members of which had committed violent crimes. His own involvement had been peaceful. However, records of his presence at demonstrations, his age and address had been kept on a database by the Metropolitan Police.

He argued successfully before a lower court that the retention of his details breached the principles of the Data Protection Act 1998 and his human right to respect for his private life, which is guaranteed by the European Convention on Human Rights. In overturning that decision, however, the Court noted that the relevant details were not intimate or sensitive and that any interference with his rights was 'minor'.

The man's details were regularly reviewed with a view to deletion if their inclusion was no longer appropriate. The Court concluded that such databases make a significant contribution to the detection of crime and a ruling in the man's favour would place a disproportionate burden on police forces and have serious consequences for effective policing.