Greenbelt, Maryland (CNN) Domestic terror suspect Christopher Hasson pleaded not guilty in federal court Monday to weapon and drug charges that prosecutors say were connected to a plot to murder Democratic and media figures.

In a brief arraignment in Greenbelt, Maryland, Hasson, a Coast Guard lieutenant, wore a maroon jumpsuit and answered several questions from Judge Gina L. Simms about the charges.

Hasson was indicted in February on charges of unlawful possession of two improperly registered silencers, possession of a narcotic opioid and possession of 17 firearms as an unlawful user and addict of a controlled substance. If convicted on all four counts, he could receive 31 years in prison.

Prosecutors say Hasson wanted to conduct a mass killing and described his white supremacist views in court documents, but have been able so far to charge him only with less serious crimes, opening the door for his lawyers to challenge the detention.

The case highlights the problem prosecutors face in bringing charges against domestic terrorism suspects, when no criminal charge for domestic terrorism exists.

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