He's been a very tough witness for the defense to cross-examine, mostly because he comes across as so composed and knowledgeable.

NPR: Witness: Enron Executives Knew of Inflated Earnings

Almost all the original physical evidence was missing, including the apparent murder weapon, and the only eyewitness to the event was the mother of both the victim and the shooter and she would no doubt be summoned as the star witness for the defense.

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That would change Mr. Pettitte's role in the trial from that of a key prosecution witness to an asset for the defense.

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