A few years ago, a co-worker of mine was traveling with his wife who had a fairly advanced case of alzheimer's and her aid. He's a very assertive person. For some reason, the aide got marked SSSS and they wanted to screen her separately. He refused, saying that his wife and her aide cannot be separated even for a minute. After some discussions, they also flagged his wife as SSSS. This was in HHMD days and so they go to her and say "raise your arm". She does nothing. So they yell it. Still nothing. My co-worker says "she has alzheimer's: she's not going to be able to respond to your commands". Their response was "so how can we screen her?". My co-worker said: "that's not my problem: it's yours. You need to figure it out. And you need to figure it out before our flight leaves". They did, but I suspect that somebody less assertive wouldn't have had the same result.