A method and apparatus for testing luggage screening equipment operators is provides. A sequence of images of contents of luggage items derived from a device that scans the luggage items with penetrating radiation are received. The image generation device is characterized by introducing a certain distortion into these images of contents of luggage items. A display device is caused to display images derived from this sequence of images. Occasionally, the display device is caused to show a simulated threat in a luggage item by displaying a combined image derived based at least in part on an image in the sequence of images and a distorted threat image. The distorted threat image was derived by applying a distortion insertion process to a reference threat image wherein the distortion insertion process tends to approximate the certain distortion introduced in the images of contents of luggage items by the device that scans the luggage items with penetrating radiation.