DNA

There has been plenty of controversy over the Police practice of taking DNA samples from everyone who is arrested, whether or not that arrest results in a charge. I too feel a bit uncomfortable about it, and certainly few other countries go anywhere near as far as we do in the UK.
However, it is a fact that many crimes have been solved by DNA technology, and I saw one last year, when a man was charged with violent rape of a stranger. After the incident, several years ago, he got clean away. Until, that is, he was picked up for a trivial theft, the computers cross-matched the samples, and that was that.
Does that justify the backdoor building of a population-wide DNA database? It's not an easy one to answer.