The following editorial appeared in Monday's Washington Post: On its face the proposition seems reasonable enough: Anyone who pleads guilty to a federal crime must give up the right to use DNA evidence in the future to challenge that conviction. This Bush-era policy would work just fine in a perfect world, where only those who actually committed crimes pleaded guilty to those offenses. But the facts show that this is not always the case. Defendants sometimes cop to a plea for reasons having nothing to do with guilt. Some are coerced or intimidated into a confession and subsequent plea bargain. Others accept a plea offer if it provides for a much lighter sentence than could be expected if convicted at trial. In short, not everyone who pleads guilty is guilty -- and prosecutors understand this. Yet according to The Post's Jerry Markon, the Bush Justice Department lobbied strenuously during the early part of this decade against legislation to assure inmates of access to post-conviction DNA evidence that could prove their innocence. When the bill appeared on the verge of passing, the administration succeeded in jamming through a provision that allows defendants to waive that right. Prosecutors in the Bush administration were then instructed to insist on such waivers when negotiating a plea bargain. While not all U.S. attorneys in the country went along, many routinely abided by the mandate, including federal prosecutors in the District of Columbia and in Alexandria, Va. Attorney General Eric J. Holder Jr. has called for a re-examination of the Bush policy -- and rightly so. DNA evidence has become an invaluable tool in the criminal justice system, providing prosecutors, defendants and victims with more certainty about guilt or innocence. The technology has been used to prove the innocence of some 240 or so wrongly convicted people, including some who had entered guilty pleas and some who were sentenced to death. It has been used countless more times to put actual offenders behind bars. It takes a special kind of callousness and disregard for the truth to insist that a defendant give up his rights to scientific tests that could definitively prove guilt or innocence. Mr. Holder should rebuff this jaded approach to justice by throwing out the Bush policy as soon as possible. 