Why Not Test Everything?

Balko uses Henry Skinner's case to lobby for the mandatory DNA testing of crime scene evidence:

Skinner's case raises a fundamental question about how police and district attorneys investigate and prosecute crimes: Why wasn't this evidence tested before Skinner's trial? And why hasn't it been tested since? The answers lie in the adversarial nature of our criminal justice system. There are times when neither the prosecution nor the defense is particularly interested in discovering the truth. That's where policy makers need to step in. In cases like Skinner's, they should establish a common-sense rule: When there is biological evidence at the crime scene, all of that evidence should be sent for DNA testing. No exceptions.