A holder (12) for checking non-compliance of a blister package has a pocket (60) into which the blister package is inserted. The front of the pocket is a transparent plate (128). Rectangular openings of wells (133) in the front face of the box (121) are positioned behind the blisters of the blister package. Each well contains light-sensitive elements (134). Non-compliance occurs when a blister of a used blister package is in an unopened condition. The sensing elements (134) detect this by ambient light in the pocket not reaching the elements. An electrical circuit in the box (121) monitors the elements (134) and provides a signal indicating a non-compliance condition if a blister in the returned package is unopened. Information identifying the unopened blister is stored in the circuit. A variable light source can be provided.
