I think, what it comes down to, is that what every prosecutor, lawyer, solicitor, etc... wants are winnable cases. Unfortunately, due to shows such as CSI, many members of the public honestly believe that DNA evidence is fool-proof. While this is certainly not the truth; law professionals are more then willing to run with no other evidence because they can win those cases. So, until the general public get's inclined to increase their level of knowledge in this area (so not likely) more innocent people will be put behind bars due to lazy bureaucrats.