What is the history of rules requiring prosecutors to disclose evidence?
<p>I was surprised to discover that <a href="https://en.wikipedia.org/wiki/Brady_v._Maryland" rel="nofollow noreferrer"><em>Brady v. Maryland</em></a> was decided as recently as 1963.  Not knowing enough about the context in which it was decided, I am having trouble understanding exactly what changed as a result of the decision.</p>

<p><em>Brady</em> only addresses the disclosure of <em>exculpatory</em> evidence, and specifically in the context of sentencing rather than determination of guilt.  (The case was remanded for resentencing consistent with the decision, but the conviction was affirmed.)  I have not been able to find out what the rule was in the U.S. prior to <em>Brady</em>.  Pre-<em>Brady</em>, was there any duty to disclose exculpatory evidence?  Is <em>Brady</em> establishing this duty for the first time, or is <em>Brady</em>'s contribution to extend this duty to apply to evidence that might only affect sentencing?  Or it it significant for some other reason?  If there was a Pre-<em>Brady</em> duty to disclose exculpatory evidence, when was it established?</p>

<p>I have read <a href="http://caselaw.findlaw.com/us-supreme-court/373/83.html" rel="nofollow noreferrer">the original decision</a> but I find it hard to interpret, so here I am.</p>

<p>I imagine that the rules about disclosure of <em>inculpatory</em> evidence must be much older and much stricter.  Is this so?  What are the major landmarks on this topic?</p>

<p>In 1935, the Supreme Court held in <a href="http://caselaw.findlaw.com/us-supreme-court/294/103.html#112" rel="nofollow noreferrer">Mooney v. Holohan</a> that the prosecution lying about evidence betrays the duty of the prosecutor to seek justice.  As such, any evidence that could be in the defense's favor must be revealed to the defense (the defense is entitled to see all evidence against the accused that will be used in trial... and need not turn over evidence that supports the prosecution).  Thus, withholding evidence that does not support the prosecution is a lie of omission and thus still lying in court.  When this happens, a new trial must be conducted with all new evidence in play.</p>
<p><em>Brady</em> extends this as Brady was convicted on Felony Murder (i.e. Brady was committing another crime and due to this, someone was killed) and given the death penalty.  In this case, while Brady admitted that the victim died during the course of the robbery, he maintained he should not be sentenced to death as it was solely the actions of his partner, Donald Bobit, that lead to to the victim's death.  The court did not find evidence of this statement and sentenced Brady and Bobit to death.  Evidence supporting Brady (a confession by Bobit that he and he alone killed the victim) was withheld from Brady's defense at the time of sentencing and the state held on appeal that this was not a violation of <em>Mooney</em> as Brady was still guilty of the accused crime.</p>
<p>The Supreme Court overturned this and ruled that evidence of a mitigating factor could be material to the sentencing still counts as exculpatory evidence and the prosecutor must turn it over.  Brady's sentence was vacated, but he was still guilty of the crime he was accused of (committing the original crime of Robbery where someone died during the course of his actions, even though he had no direct hand in that person's death).  In effect, Brady was still guilty but not deserving of the Death Sentence, just as he claimed in his appeal.</p>

united-states evidence us-supreme-court legal-history prosecution