State police say Amber Cummings, 31, shot James Cummings, 29, in their High St. home in Belfast back in December.
Cummings pleaded not guilty and not criminally responsible because of mental disease or defect in Belfast District Court.
Officials were initially calling this a domestic homicide, there are reports that Amber Cummings was violently abused by her husband.
James Cummings has been linked to white supremacist groups, and police found radioactive materials and instructions for building a ":dirty bomb": in the High St. home.
Amber Cummings is being held pending a bail hearing late this week or early next week.