There are so many ways and so many reasons that exculpatory evidence is hidden from the defense that sometimes I forget how profoundly disturbing it is. This article from last week in USA Today, details a pattern of misconduct in the Department of Justice. It's an astounding amount of affected cases if you add back into the mix the cases they excluded because the courts found it was "harmless error" or because the trial judge didn't sufficiently reprimand.
But the truth is that most of the time exculpatory evidence is kept hidden with the participation of the judiciary and/or the legislature. For example, in Washington County, if the DA names a person as a victim and sends us a letter saying that person doesn't want to talk to us, then we are barred from having any contact, even indirect, with that person. We can't confirm that they don't want to talk to us. We can't follow up later to see if they changed their mind. We can't leave a card for them to call us if they do change their mind. If we do any of those things, we will be held in contempt of court, by order of the Criminal Presiding Judge. The person named by the DA has a right to remain silent that far exceeds the right accorded to defendants in the Constitution. This "victim's right" is only limited by the DA's sense of fairness. They can, and have, named multiple family members and other folks as victims and sent us "the letter". This prevents the defense from interviewing crucial witnesses but it can also prevent us from investigating or viewing evidence in their possession.
Of course there's also the grand jury secrecy provisions that allow the DA to subpoena and interview witnesses under oath without ever telling us what they said or even giving us the notes.
There's all the internal police bureau information on individual officers that is impossible to get unless you can demonstrate that you already know something about what's in the file. We had a case recently where we got access because, by pure luck, we found out about one of the officer's files from a civil attorney who had a case collaterally involving that officer. It turns out, once we got the file, that were a bunch of eyewitness statements for our case that were incredibly helpful to us. So helpful the case was ultimately dismissed. But we never would have found out about the information but for the luck. And the County fought us the whole way from getting access to that evidence.
The list goes on and on. And we keep fighting the good fight, trying to get all the evidence we can to defend the accused even when it seems like the whole world is crushing down upon them.