The answer to this question is slightly subtle, but the relevant law is 50 E.

E. Information from a Penalty Card
1. Information derived from a penalty card and the requirements for playing that penalty card are authorized for all players for as long as the penalty card remains on the table.

West is entitled to know that East has the AS, and that they must play the AS if legal; while it is on the table.

2. Information derived from a penalty card that has been returned to hand [as per Law 50D2(a)] is unauthorized for the partner of the player who had the penalty card (see Law 16C), but authorized for declarer.

West now has to forget that East had the AS, however South is still entitled to the knowledge.

3. Once a penalty card has been played, information derived from the circumstances under which it was created is unauthorized for the partner of the player who had the card. (For a penalty card which has not yet been played, see E1 above.)

If the AS is played to a trick (say South allows any lead; and West leads a Spade), then West isn't allowed to know that East has a S holding they'd lead the A from; rather than one they'd win the A in 3rd from [many pairs would lead the A from AK, but playing third in hand win with the K instead -> winning with the A would 'deny' the K].

4. If following the application of E1 the Director judges at the end of play that without the assistance gained through the exposed card the outcome of the board could well have been different, and in consequence the non-offending side is damaged (see Law 12B1), he shall award an adjusted score. In his adjustment he should seek to recover as nearly as possible the probable outcome of the board without the effect of the penalty card(s).

One would need to take West aside and ask them 'why' they switched to a Spade. If there are valid bridge reasons (authorised information) that duplicate the unauthorised information; and no other logical alternatives then you can allow a S switch. One needs to be careful here, as sometimes they will switch to a non-S to set up tricks there because they know it's safe because partner has the AS to stop the suit running. So you need to carefully consider how logical the defence is, both in a vacuum and with the knowledge that partner has the AS.

Hope that makes sense

Thanks again Brad, your input is extremely helpfull

I agree with Brad's points 1-3 but not 4.

I would not use 50E4 when there is unauthorised information. I would only use it when the non-offending side is damaged but the exposed card is authorised information under 50E1. Unauthorised information is still dealt with under 16B.

When there is unauthorised information, it does not matter what West's personal reasons are. All that matters is whether there are other logical alternatives, and what is suggested by the unauthorised information. Those can only be determined by analysing at the hand not by asking West what they were thinking.

I agree, against myself. Good catch

(This is what happens when I'm answering these questions at work and pre-coffee).