"It ought now be accepted, in our view, that certain decisions involved in the prosecution process are, of their nature, insusceptible of judicial review. They include decisions whether or not to prosecute .., to enter a nolle prosequi .., to proceed ex officio .., whether or not to present evidence .. and, which is usually an aspect of one or other of those decisions, decisions as to the particular charge to be laid or prosecuted .. . The integrity of the judicial process - particularly, its independence and impartiality and the public perception thereof - would be compromised if the courts were to decide or were to be in any way concerned with decisions as to who is to be prosecuted and for what .. .
A decision by a prosecutor to accept a plea to a lesser charge .. is a decision not to proceed, or, more precisely, not to present evidence on the more serious charge in the indictment and, at the same time, a decision as to the charge which is to proceed. It is insusceptible of judicial review. Subject to two qualifications, judicial review is precisely what is involved in a court's rejection of a plea which has been accepted .. ."