The motion, filed in South Carolina federal court, questions whether Roof's attack was plotted and carried out wholly within the state, and therefore not a federal case, as well as whether the hate crimes he was convicted of were punishable by death.
"A finding in his favor on this motion would resolve the case, since he would not challenge further the resulting sentences of life in prison without the possibility of release," the lawyers wrote.
Roof was sentenced to death last month after he was convicted of hate crimes in federal court. He killed nine black churchgoers during a bible style at the Emanuel African Methodist Episcopal Church in Charleston in June 2015.
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