A Boston man has admitted guilt in federal court for unlawfully possessing a machinegun. James Thelwell-Mullen, aged 32, entered the plea before U.S. District Court Judge Allison D. Burroughs. The sentencing is scheduled for July 29, 2025. Thelwell-Mullen was indicted by a federal grand jury in July 2024.
In a case stemming from events on or around April 28, 2023, Thelwell-Mullen was found to have a machinegun conversion device, commonly known as a "Glock switch." This device is designed to convert a Glock semi-automatic pistol into an automatic firearm. Court documents reveal that during a search of Thelwell-Mullen’s residence in Boston, authorities recovered a machinegun conversion device, two privately made firearms, ammunition, firearm magazines, other accessories, and a plastic bag containing fentanyl. Additionally, messages on Thelwell-Mullen’s phone suggested he was involved in selling these conversion devices.
The charge carries a potential sentence of up to 10 years in prison, a supervised release period of three years, and a fine that could reach $250,000. Federal district court judges impose sentences following the U.S. Sentencing Guidelines and considering other legal factors.
The announcement was made by United States Attorney Leah B. Foley, James M. Ferguson, Special Agent in Charge of the Bureau of Alcohol, Tobacco, Firearms and Explosives, Boston Field Division, and Boston Police Commissioner Michael Cox. Assistant U.S. Attorney Elianna J. Nuzum of the Criminal Division is handling the prosecution.
