What we have here is a guy who certainly cannot speak or make intelligible physical actions, but someone has rigged up some sort of assisted communication ouija board and tells us what this man is supposedly saying. I recall a Law and Order ep from the mid-90s where some quack child psychiatrist was accused of abuse, and his defense was a severely retarded noncommunicative boy who supposedly had been taught to communicate with such a device, by said quack. His mother certainly very much wanted to believe her son was not the mental vegetable she had always thought he was, but, in order to prosecute the man for having caused the death of another such boy in his facility, McCoy was forced to put the young man and his mother, using their 'device, o n the stand, and examine him to see what he really 'knew'. The results were predictable. I am not necessarily saying there is nothing to this Belgian story, but how can it be objectively verified?
The same way they did on L&O. Show patient picture, don't show facillitator, ask patient what is in the picture.