Whether the continued retention of the DNA, fingerprints and a photograph of GC and of the DNA, fingerprints and information on the police national computer in respect of C, violates their rights under Article 8 of the European Convention on Human Rights.It's significant because the European Court of Human Rights ruled in 2008, in the case of S. and Marper v UK, that the systematic blanket indefinite retention, by the police, of the DNA of people not charged or convicted of a crime, was in breach of of Article 8 of the European Convention on Human Rights relating to respect for privacy.
In the wake of the decision the New Labour UK government essentially decided to ignore the judgement, repeatedly procrastinating and supporting the continuence of the illegal practice of retention. The Association of Chief Police Officers, reportedly told chief constables to ignore the ruling. The Labour government also made various attempts to spin stories to the effect that they were doing something to address the ruling whilst going to what some would consider extraordinary lengths to avoid doing so. Comedian Mark Thomas has been one of the few who has managed to arrange to have his DNA and fingerprints removed from police records, since the S. and Marper decision.
The coalition goverment came in on the promise of directly quashing many of the liberty bashing laws and behaviours of their immediate predecessors but as Terri Dowty, amongst others, has recently pointed out, action in relation to those promises has been slow in manifesting itself. The Metropolitan Police's likely defeat on the issue before the UK Supreme Court and the government's response to that will be another indicator of whether or not they have the strength to follow through on promises easily made whilst in opposition.
I'd recommend also Eoin O'Dell's commentary on the same.