From the time Jessica is seen reading in her room when she hears the shot up until immediately after the shooting with the family gathered around with the detective questioning Eugene, Jessica's pearl necklace disappears/reappears between shots.
Toward the finale, Jessica is wearing a dark dress with earrings and pearls. She goes into the kitchen, and the pearls are gone, she is bare necked. A few moments later, she is in the living room and wearing the pearls again.
Several characters complain about the heat and lack of a breeze while in the house, yet no windows are open.