The sole reason I can see for not permitting a DNA database is if access is permitted to researchers or insurance companies -- esp. the latter. It might well be possible to determine a genetic predisposition for a disease or medical condition and insurance refused on that grounds.

As for sloppy lab work -- yes, it happens. And it's unacceptable. (I could add 'and it's Texas,' but I won't.) There is no answer, no recompense which can be made for such, but humans ARE fallible (even in the machines we create). All we can do is try to like hell to insure that no one is ever convicted on sloppy lab work, shoddy detective work, prejudice, or other such reasons.