Denville man pleads guilty to storing 109 vials of homemade explosives

A Denville man pleaded guilty on Monday to storing 109 vials of homemade explosives in his backyard shed.

Joseph Rizos, a 37-year-old process engineer, is likely to face three years in state prison when sentenced in January.

That’s what Morris County Assistant Prosecutor Noelle Fiorentino is recommending, under a deal in which Rizos agreed to plead to a second-degree count of recklessly risking widespread injury or damage, which can carry a sentence of 10 years.

Other charges of unlawful possession of assault firearms, destructive devices and large-capacity magazines would be dismissed if the agreement is accepted by Superior Court Judge Ralph Amirata.

Rizos still faces federal charges from his arrest on June 24, 2026. Authorities say a search of his Avondale Road residence recovered laboratory equipment, instructions for manufacturing explosives, chemicals and containers of suspected explosives, tactical gear, and 17 firearms.

At the time, Morris County Prosecutor Robert Carroll said the alleged cache was capable of “mass destruction” while “matters of national significance are transpiring in Northern New Jersey”—presumably, a reference to soccer’s World Cup.

No motive was given by Rizos on Monday in Morristown. Appearing before Judge Amirata, he calmly admitted storing 109 vials of “homemade explosives,” consisting of RDX, PETN, picric acid and TNT.

Authorities have called them military-grade chemicals that can be extremely volatile. They also can be hard to detect, making them explosives of choice for terrorists. Neighbors were evacuated during the search.

Defense attorney Robert Neary previously noted Rizos has no prior criminal record, describing him as a “chemistry savant” akin to Bill Nye the Science Guy.

What prosecutors called blasting caps, Neary has suggested, simply were thermocouple probes Rizos used for monitoring compost in his mother’s garden. The lawyer also has claimed the vials contained water and were incapable of detonating.

Fiorentino said she will ask for the state sentence to run concurrently with any sentence Rizos may receive on the pending federal charges. In the meantime, Amirata ordered Rizos’ continued detention at the Morris County Jail.

The Justice Department has accused Rizos of unlawfully receiving and storing explosive materials, and possessing plastic explosives without a detection agent. Federal prosecutors  allege he bought explosives, related materials and lab gear online between April 2020 and June 2026 and illegally stashed everything at his Denville home.