Why do a few devious prosecutors withhold exculpatory evidence which should be turned over to the defense attorney in criminal cases? Other than sheer laziness or overzealousness, I really don't understand why prosecutors conceal such evidence! But as a former career prosecutor, I believe an "open file" discovery policy is not only more fair to the defendant, but also it helps the prosecutor, too. Here's why!
The Supreme Court held in Brady v. Maryland that the government must turn over to the defense lawyer any "exculpatory evidence;" that is, any evidence which tends to exculpate or show the defendant may be innocent. Many appeals of convictions address whether or not the prosecutor complied with this rule. As a former prosecutor, I found that, by providing "open file" discovery of my entire file to the defense lawyer, (other than sensitive victim or informant information), I could avoid such questions on appeal.
I also learned that, by turning over a copy of my file, and showing the criminal defense lawyer that I had a great case, it also helped me to obtain guilty pleas more quickly.
Finally, I learned that by providing "open file" discovery to the defense attorney, I could sleep well at night! In other words, I could be confident that I was ensuring the defendant a fair day in court!
So, in my opinion, just as honesty is generally the best policy, "open file" discovery in criminal cases is the best policy, too! Devious prosecutors should wise up!