(a) In general. — (1) In a criminal proceeding, the prosecution shall, upon written demand of a defendant filed in the proceedings at least 5 days prior to the trial, require the presence of the forensic toxicologist or forensic chemist, or any person in the chain of custody as a prosecution witness.
(2) The provisions of §§ 4330 and 4331 of this title concerning prima facie evidence do not apply to the testimony of that witness.
(3) The provisions of §§ 4330 and 4331 of this title are applicable in a criminal proceeding only when a copy of the report or statement to be introduced is mailed, delivered or made available to counsel for the defendant or to the defendant personally when the defendant is not represented by counsel, at least 10 days prior to the introduction of the report or statement at trial.
(b) Witness for defense. — Nothing contained in this subchapter shall prevent the defendant from summoning a witness mentioned in this subchapter as a witness for the defense.