David Matusiewicz has pleaded not guilty to federal conspiracy and stalking charges regarding his deceased ex-wife Christine Belford and her family.
The son of the Delaware courthouse shooter will remain in custody pending a trial.
David, along with his mother, Lenore Matusiewicz, and his sister, Amy Gonzalez, is charged with one count of conspiring to commit interstate stalking and cyberstalking, two counts of interstate stalking, and one count of cyberstalking of Belford.
Belford and her friend, Laura Mulford were gunned down by Thomas Matusiewicz in the lobby of the New Castle County Courthouse in February. Thomas took his own life following a shootout with Capitol Police.
Belford and David had engaged in years of a bitter custody battle over their three daughters.
In 2007, David and Lenore kidnapped the three children and hid out in South America for nearly two years. They were arrested in 2009 and both served prison time and were ordered not to contact Belford or the children.
David Weiss, acting U.S. attorney for the district of Delaware, brought charges that Matusiewicz had stalked, harassed and planned to harm or kill Belford since 2009.
All three defendants face a maximum sentence of life in prison, a $250,000 fine for each count and a three-to-five-year term of supervised release.
Lenore and Gonzalez were arrested in Texas and will be extradited to Delaware.