After the 23 October street riots, the police asked Budapest's hospitals to provide information about anybody they had treated during the unrest. The police clearly intended to interview some of the injured as witnesses in the hope that they might later be identified as rioters with the aid of photographic and video evidence.

But it is not clear that the police have the right to ask for information about patients. Adam Foldes, a lawyer for the Hungarian Civil Liberties Union, explains: "Concrete information about a particular person can only be requested for a specific, legal reason." Mass data gathering is mostly illegal, he says, and police would only be entitled to request hospital information about an individual if an investigation were already in progress and the data they sought could be used as evidence. He continues: "It does not work the other way round: it is impossible to collect the data first and then look for suspects among that mass of information."

But Tibor Jarmy, a spokesman for Budapest Police, disagrees. He claims the law on criminal procedure allows police to ask for information about anybody if they are investigating a crime perpetrated by an unknown individual. Andras Kristof Kadar, a lawyer for the Hungarian Helsinki Committee, says: "The relevant paragraph of the law that only such personal data can be requested that is essential to achieving specific aims - and this can be twisted to mean anything at all." It is actually more complicated than this, he says, since information can only be requested about specific suspects. Nonetheless, he believes the police can, by insisting on the need to interrogate witnesses, demand information about people who ended up in hospital.

If the witness then becomes a suspect - and it is for this very reason that the police have asked for information about the injured - the information obtained from the hospitals cannot be used as evidence, because, Kadar says, "the paragraph in question makes it clear that illegally obtained evidence cannot be used in trial." The police are thus within their rights to use hospital information to identify witnesses, but the same information will be worthless if the witnesses become suspects.

Hospitals are uncertain. Peterfy Sandor utca hospital immediately turned to the data protection commissioner on receiving the police request for information. The commissioner then said the police request was unacceptable as it stood. The police sent a new letter, which this time specified the nature of the case the police were working in and the laws under which they were requesting the data. Attila Peterfalvi, the data protection commissioner, once again found that the police letter was irregular. Peterfalvi has stated that while it is quite usual for a witness to become a suspect, it is an abuse of the law for this to happen as a result of mass data gathering.

Information can be demanded of the hospitals if there is good reason for doing so and if the data is destroyed after use. In practice, the police will have to collect that information and get closer on the trail of the perpetrators. But arriving at hospital with a head injury last Monday is not evidence of anything much at all.