(a) In any criminal prosecution brought by the United States, no statement or report in the possession of the United States which was made by a Government witness or prospective Government witness (other than the defendant) shall be the subject of subpena, discovery, or inspection until said witness has testified on direct examination in the trial of the case.

(b) After a witness called by the United States has testified on direct examination, the court shall, on motion of the defendant, order the United States to produce any statement (as hereinafter defined) of the witness in the possession of the United States which relates to the subject matter as to which the witness has testified. If the entire contents of any such statement relate to the subject matter of the testimony of the witness, the court shall order it to be delivered directly to the defendant for his examination and use.

(c) If the United States claims that any statement ordered to be produced under this section contains matter which does not relate to the subject matter of the testimony of the witness, the court shall order the United States to deliver such statement for the inspection of the court in camera. Upon such delivery the court shall excise the portions of such statement which do not relate to the subject matter of the testimony of the witness. With such material excised, the court shall then direct delivery of such statement to the defendant for his use. If, pursuant to such procedure, any portion of such statement is withheld from the defendant and the defendant objects to such withholding, and the trial is continued to an adjudication of the guilt of the defendant, the entire text of such statement shall be preserved by the United States and, in the event the defendant appeals, shall be made available to the appellate court for the purpose of determining the correctness of the ruling of the trial judge. Whenever any statement is delivered to a defendant pursuant to this section, the court in its discretion, upon application of said defendant, may recess proceedings in the trial for such time as it may determine to be reasonably required for the examination of such statement by said defendant and his preparation for its use in the trial.

(d) If the United States elects not to comply with an order of the court under subsection (b) or (c) hereof to deliver to the defendant any such statement, or such portion thereof as the court may direct, the court shall strike from the record the testimony of the witness, and the trial shall proceed unless the court in its discretion shall determine that the interests of justice require that a mistrial be declared.

(e) The term "statement", as used in subsections (b), (c), and (d) of this section in relation to any witness called by the United States, means—

(1) a written statement made by said witness and signed or otherwise adopted or approved by him;

(2) a stenographic, mechanical, electrical, or other recording, or a transcription thereof, which is a substantially verbatim recital of an oral statement made by said witness and recorded contemporaneously with the making of such oral statement; or

(3) a statement, however taken or recorded, or a transcription thereof, if any, made by said witness to a grand jury.