PAINESVILLE, Ohio (AP) --A prosecutor tells a jury that a Lake County man started an affair with his teenage foster daughter and then conspired with the girl to kill his wife.

Prosecutor John O'Donnell told a Lake County jury on Monday that 43-year-old Kevin Knoefel even instructed his foster daughter how to stab 41-year-old Lisa Knoefel to cause the most internal damage.

O'Donnell said Kevin Knoefel wanted his wife out of the way and was afraid he'd lose custody of their 3-year-old daughter if they divorced.

Knoefel is charged with murder conspiracy.

Lisa Knoefel was killed on Nov. 16, 2012, allegedly by then-17-year-old Sabrina Zunich. Defense attorney Michael Connick told jurors that Zunich, now 19, is mentally ill and acted alone.