Incident location, Long Island
What Happened
A 24-year-old Nesconset motorcyclist is dead and a St. James man faces a drunk driving charge after a violent early-morning collision at the intersection of Nesconset Highway and New Moriches Road in Stony Brook at approximately 12:22 a.m. on Saturday, January 3, 2026. According to Stanley Law Offices, which cited the Suffolk County Police Department, the crash claimed the life of Jerry Diaz and resulted in the on-scene arrest of the pickup truck driver.
Jerry Diaz was operating a 2022 Honda CRF450RL motorcycle in the westbound direction on Nesconset Highway (Route 347) when the crash occurred. At the same time, 25-year-old Mark Anthony Giordano of St. James was driving a 2017 GMC pickup truck northbound on New Moriches Road. As Giordano attempted to execute a left-hand turn from New Moriches Road onto westbound Nesconset Highway, he crossed into the path of Diaz’s oncoming motorcycle. The result, according to the Suffolk County Police Department as reported by Stanley Law Offices, was a violent collision that left the motorcyclist with fatal injuries.
Jerry Diaz was pronounced dead at the scene. The official determination was made by a physician assistant from the Office of the Suffolk County Medical Examiner, who responded to the crash site. Diaz was a resident of Nesconset, a hamlet just a few miles from where the fatal crash took place on Route 347.
Mark Anthony Giordano, 25, was uninjured in the crash. Despite escaping the collision without physical harm, Giordano did not leave the scene a free man — he was arrested on the spot and charged with Driving While Intoxicated (DWI). According to reporting by Stanley Law Offices citing police, Giordano’s intoxication is believed to have been a direct contributing factor in his failure to properly yield to Diaz’s oncoming motorcycle before making the left-hand turn.
Following the collision, both the 2022 Honda CRF450RL motorcycle and the 2017 GMC pickup truck were impounded by authorities for safety checks — a standard procedure in fatal crash investigations that allows investigators to evaluate the mechanical condition of each vehicle and rule out equipment failure as a contributing factor. The crash drew a response from multiple agencies in the early morning hours on what was a frigid winter Saturday on Long Island.
Location & Road Context
The crash took place at the intersection of Nesconset Highway (Route 347) and New Moriches Road in Stony Brook, a heavily traveled stretch of roadway in central Suffolk County. Nesconset Highway is a major east-west commercial and commuter corridor running through multiple hamlets in the Town of Smithtown, connecting communities from Port Jefferson Station in the east toward Hauppauge and beyond to the west. The corridor carries substantial traffic volume around the clock, and intersections along Route 347 — particularly those involving left-hand turns across oncoming lanes — have historically been the sites of serious accidents on Long Island.
New Moriches Road intersects Route 347 at a point that requires northbound drivers to make a sweeping left-hand turn across westbound highway lanes. At 12:22 a.m., traffic volumes would have been lower than daytime levels, but any motorcycle traveling at highway speed in the dark would present a significant hazard to a turning driver — especially one who was allegedly impaired. The area is within close proximity to several late-night establishments, making it a corridor that Suffolk County law enforcement monitors for impaired driving activity.
Investigation & Legal Proceedings
The investigation into the fatal crash is being handled by the Suffolk County Police Major Case Unit, an elite investigative division tasked with handling serious and fatal collisions across Suffolk County. The involvement of the Major Case Unit signals the gravity of the incident and indicates that investigators are conducting a thorough review of all evidence, including physical crash data, toxicology results, and vehicle inspection findings from the impounded vehicles.
Mark Anthony Giordano was charged at the scene with Driving While Intoxicated. Under New York law, a DWI charge carries the potential for significant criminal penalties, and when a death results from an intoxicated driver’s conduct, prosecutors may pursue elevated charges — such as Vehicular Manslaughter — as the investigation progresses. New York Vehicle and Traffic Law § 1141 requires that any driver intending to make a left turn must yield the right of way to oncoming vehicles close enough to constitute an immediate hazard. Giordano’s alleged failure to yield while operating under the influence forms the legal foundation of both the criminal case against him and any potential civil wrongful death action by the Diaz family. The investigation was described as active and ongoing as of the initial reporting.
Broader Impact
This fatal crash on Route 347 is not an isolated event in the Stony Brook area. Long Island Traffic has previously reported a DWI crash that killed a 24-year-old motorcyclist in Stony Brook in September 2025 and, more recently, a teen charged with DWI after a Long Island Expressway crash that seriously injured a Stony Brook passenger in April 2026. The pattern of DWI-involved crashes in and around the Stony Brook corridor underscores the recurring danger that intoxicated drivers pose to motorcyclists, who are among the most vulnerable road users and offer virtually no barrier between themselves and a striking vehicle. In New York State, a conviction on a standard DWI charge carries a minimum six-month license revocation and fines up to $1,000 for a first offense — figures that can escalate dramatically if prosecutors upgrade the charges to reflect the fatal outcome of this collision.