If facts were suppressed for example and they came out proving the guilt of the defendant who walked the first time around why can't there be a retrial USING ALL THE EVIDENCE or just put the guilty party in prison? Why shouldn't wrongs be righted when they can?
Or contrarily evidence was faked to convict a person who was innocent. Later on that is proven beyond a shadow of a doubt so no trial would be needed to release an innocent person right?