Federal Rule of Civil Procedure 50 sets forth the procedural requirements for challenging the sufficiency of the evidence in a civil jury trial and establishes two stages for such challenges--prior to submission of the case to the jury, and after the verdict and entry of judgment. Rule 50(a) allows a party to challenge the sufficiency of the evidence prior to submission of the case to the jury, and authorizes the District Court to grant such motions at the court's discretion: '(a) Judgment as a Matter of Law. '(1) If during a trial by jury a party has been fully heard on an issue and there is no legally sufficient evidentiary basis for a reasonable jury to find for that party on that issue, the court may determine the issue against that party and may grant a motion for judgment as a matter of law against that party with respect to a claim or defense that cannot under the controlling law be maintained or defeated without a favorable finding on that issue. '(2) Motions for judgment as a matter of law may be made at any time before submission of the case to the jury. Such a motion ...