MANDAN, N.D. (AP) — A man sentenced to life in prison for killing four people at a North Dakota business in what authorities say was one of the most heinous crimes in the state’s history is appealing his conviction.

An attorney for Chad Isaak argues the man’s conviction should be reversed because of errors during jury selection and violations of Isaak’s right to a public trial.

In a brief filed with the North Dakota Supreme Court on June 30, defense attorney Kiara Kraus-Parr argues that Isaak’s rights were violated because no record was made of some conferences involving the judge and attorneys held before and during the trial. Also, the appeal states public access to court documents and autopsy photos was improperly closed, and that jurors were dismissed outside Isaak’s presence.

Prosecutors have until July 30 to file a response, the Bismarck Tribune reported.

A jury in August found the 48-year-old Washburn chiropractor guilty of killing RJR Maintenance and Management co-owner Robert Fakler, 52; and employees Adam Fuehrer, 42; Bill Cobb, 50; and his wife, Lois Cobb, 45.

The four were shot and stabbed on April 1, 2019, inside the property management company’s building in Mandan. Investigators said the victims were stabbed more than 100 times, total.

A clear motive has not been established for the killings.

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