Retention by the police of information about a suspect can be a breach of the suspect's right to privacy: S and Marper v United Kingdom  ECHR 1581 (4 December 2008).
This case concerns fingerprints and DNA samples taken by the police. Neither of the applicants was convicted and both requested destruction of these records. The police refused.
The Grand Chamber held that retention of the information in such circumstances was a breach of the applicants' rights to privacy and that vindication was achieved by the Court's finding of a violation in view of the resulting obligation on the UK to secure the rights of the applicants and of persons in their position.
This decision applies to samples taken directly from suspects. That sort of information collection is now the subject of legislation in many jurisdictions. In New Zealand we have the Criminal Investigations (Bodily Samples) Act 1995. The bracketed words highlight its focus which is the obtaining of invasive intimate samples, if necessary by force; it does not provide a code for the obtaining of such information by other non-invasive means: R v Cooper CA381/00, 19/2/01. DNA from clothing seized during execution of a search warrant was used in that case to establish that the accused was the father of the victim and of her child. The Court of Appeal held that this investigatory technique was not unreasonable, and also that it was lawful, meaning that the Act did not apply to this means of gathering information.
There is in NZ no regulatory regime governing the retention and destruction of information obtained by indirect means such as those used in Cooper. Obviously, where the suspect is convicted, permanent retention of the information may be justified, as it is under the Act for convictions of specified offences. But for people like the applicants in S and Marper, more rules are needed.