State v. Arndt, No. 95396-1 (December 5, 2019), Washington Supreme Court.
Brief: The trial court’s rulings limiting the testimony of the defendant’s expert witness did not violate her Sixth Amendment right to present a defense and were well within the court’s discretion. The defendant’s convictions of both first degree aggravated murder and first degree arson did not violate double jeopardy protections, because when two crimes have separate purposes and effects, multiple punishments are allowed.
Translation: A court has a lot of power to limit an expert witness’s testimony without violating the 6th amendment. A single act can violate two laws when they have distinct reasons and effects.