Keep in mind that we're talking about evidence in the possession of the prosecutor. If you already know about it, it isn't Brady material. It only falls under Brady if you don't know it exists.
But, if you don't know it exists, how can you be certain the prosecutor is providing it to you? How do you know the prosecutor doesn't just ignore it and move on to the next witness? And, even more important, how do you know whether this material you don't know exists, is material to the case?
Recently we have seen special prosecutor Henry Schuelke castigate federal prosecutors for their role in not turning over exculpatory evidence to former U.S. Senator Ted Stevens' attorneys in the run-up t his trial. We've also seen the Chief Judge of the Texas Supreme Court (the highest civil court in the state) call for an inquiry into whether a former Williamson County DA (now a state district judge) violated the law by failing to turn over exculpatory evidence in a 1987 case.
Nancy Gertner and Barry Scheck have a proposal to put more pressure on prosecutors to follow Brady:
The two cases present a simple solution for dealing with prosecutorial misconduct: Thirty days before trial, or at some reasonable time, the trial judge should convene a conference and issue a specific order directing prosecutors to produce all evidence that "tends to negate the guilt of the accused or mitigate the offense," as required by the American Bar Association's ethics rules. This should include the requirement that prosecutors contact the relevant law-enforcement personnel to make certain all such evidence is disclosed as soon as possible.Whether issuing such an order will resolve the issue is a question in need of an answer. First, we will continue to have the very real problem that there is no way to know what material the prosecutor has at his disposal unless the prosecutor (or a whistleblower) is willing to hand it over. Second, who makes the determination whether the evidence is material? If the prosecutor doesn't think the evidence is material - you'll never see it. Third, how would the order be enforced? Most cases involving Brady violations are old. The nature of the violations only come to be known years after the fact when someone is sifting through old files.
Rare would be the case in which a Brady violation surfaced at trial. The only way defense counsel could point out the violation was to produce the exculpatory evidence - and if the defense is in possession of the exculpatory evidence, Brady doesn't apply.
So, while Ms. Gertner and Mr. Scheck's proposal is a good idea and a step in the right direction, it is by no means a solution to the conundrum that is Brady.