CEDAR RAPIDS, Iowa (AP) — A new trial has been ordered for a Cedar Rapids man who’d been convicted of stabbing to death his former girlfriend.

The Iowa Court of Appeals said in its ruling Wednesday for Nicholas Luerkens that the trial court “erred in denying the defendant’s request to submit an insanity defense instruction to the jury.”

In November 2015 a jury found Luerkens guilty of first-degree murder for killing 29-year-old Lynnsey Donald. Officials say Luerkens stabbed Donald dozens of times in a Marion parking lot on April 21, 2015, as Donald’s 7-year-old son watched. Prosecutors say Luerkens had been following Donald for months before the attack.

Defense lawyers say Luerkens was overusing an antidepressant drug, which contributed to diminished mental capacity during the attack.