D was tried for conspiring with Ronnie and William Bernacet, Ephraim Flores and Gino Romano to plant and set off a pipe bomb below a pizzeria on Nostrand Avenue in Brooklyn, and a second below a nearby laundromat. The first bomb did not explode. P claimed that the bomb planted in the laundromat had exploded as planned, and thus Ds were charged with arson in the first degree, as well as attempt. The Bernacet brothers were tried first. Officer Daniel Kiely, a member of the Bomb Squad, testified that a thorough inspection of the basement revealed no evidence that there had been an explosion, but asked that the case be kept open. Kiely testified that he ultimately concluded that there had been an explosion, defense counsel in summation argued that there was insufficient proof of the explosion element of first-degree arson, based on Kiely's first report. The Bernacet brothers were acquitted of the completed arson. D's counsel made a pretrial request for all reports 'by ballistics, firearm and explosive experts' concerning the laundromat explosion. A different prosecutor from the one who tried the Bernacets was trying D. In response to discovery, P sent all but Officer Kiely's first report. No questions about that first report were asked during the brief cross-examination of Kiely, and no effort was made to argue that P had failed to establish the explosion element of the top count. D's defense was that the police informant was unreliable. D was convicted on all counts. D's counsel discovered the undisclosed explosives report. D made a motion to vacate the judgment; an undisclosed explosives report was Brady material (and failure to disclose violated his due process rights under the State and Federal Constitutions) and that his trial counsel had been ineffective. P responded that there was overwhelming evidence of D's guilt. The motion was denied. D appealed. The Appellate Division concluded that defendant's Brady claim was properly raised and granted D's motion to the extent of vacating his conviction of arson in the first degree. It held that the report was exculpatory, that the prosecution violated D's constitutional right to be informed of exculpatory information known to the State, and that reversal was required 'if there is a reasonable possibility that [the undisclosed material] contributed to the defendant's conviction.' P appealed.