He used the patented soybeans for his main spring crop, but went to a local grain elevator and purchased so-called commodity seeds for a riskier, late-season crop.
Authorities said Ms. Gillespie, a mother of four adult children, was returning to her Prospect Heights apartment from a shopping trip to the local Key Food on Dec. 17, 2011, when she left the elevator at the fifth floor to find Mr. Isaac standing there.