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NEW CASTLE COUNTY, Del. (CBS) — A Delaware man sentenced to life in prison in a landmark cyberstalking case has lost his appeal in federal court.

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In 2016, David Matusiewicz, along with his mother and sister, were the first people in the country convicted of cyberstalking resulting in death.

Credit: CBS3

They allegedly harassed his ex-wife, Christine Belford, for years over a custody battle.

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In 2013, David’s father, Thomas, shot and killed Belford inside the New Castle County courthouse.

Belford’s friend also died.