If you were in court, and the evidence provided by the prosecution was acquired in such a way as to have this high a failure rate, with this many problems, it would surely be deemed inadmissable. Eg - "We've got a partial fingerprint from a piece of glass. It partially matches your little finger. As we've got nobody else to match it against, and have some juicy Labour targets to meet, we'll throw the book at you anyway. If you were on our database to start with, you MUST be evil/a terrorist/a 9-11 plotter/insert convenient gov't label here" - thrown out.
But as soon as the magic Totally Infallible™ DNA records pop out, it's another matter. Never mind the fact that so many records are missing, invalid, incorrectly entered - or that DNA isn't as reliable as it's made out to be to start with!