(based on an incident at Porthcawl Club; subsequently used in WBU Director training simulations).
[South is declarer in 5♦ having lost one trick. She doesn’t know the position of the ♣J – if a finesse succeeds a losing spade could be discarded on the remaining club. However, if it fails, East will probably return a spade, thereby declarer would then also lose two spades. She reckons that her best chance is to first lead the ♠J from dummy, tempting East to cover and felling partner’s ace – only one spade loser.]
Having won the previous trick in hand, she calls for the ♠J from dummy. West immediately states to South that she is in her hand, but that he will accept the lead from dummy and duly plays his ♠A.
The Director states that West is entitled to accept the lead, and rules that in playing the ♠A, the incorrect lead has been accepted.However the ♠A is now a penalty card and must be played at the first legal opportunity (this trick). East plays low, South follows, and West has to play his penalty card; declarer loses two spade tricks.