North is declarer in a diamond contract. West, his right-hand opponent, has won trick five by ruffing a heart. North hasn’t noticed the ruff, and thinking he has won the trick in his own hand, now leads the ♥K. East without thought, now follows with ♥7, at which point West remarks that it is in fact his lead to trick six.
The Director asks for a full explanation as to what has happened, during which North remarks that by following to his inadvertant lead out-of-turn, East has accepted it. The Director then consults his Law book, refering to Law 55
LAW 55 – DECLARER’S LEAD OUT OF TURN
A. Declarer’s Lead Accepted
If declarer has led out of turn from his or dummy’s hand then either defender may accept the lead as provided in Law 53 or require its retraction (after misinformation, see Law 47E1). If the defenders choose differently then the option expressed by the player next in turn to the irregular lead shall prevail.
So now refering to Law 53….
LAW 53 – LEAD OUT OF TURN ACCEPTED
A. Lead Out of Turn Treated as Correct Lead
Prior to the thirteenth trick , any lead faced out of turn may be treated as a correct lead (but see Law 47E1). It becomes a correct lead if declarer or either defender, as the case may be, accepts it by making a statement to that effect, or if a play is made from the hand next in rotation to the irregular lead (but see B). If there is no such acceptance or play, the Director will require that the lead be made from the correct hand (and see Law 47B).
Based on this the Director now rules that East has indeed accepted North’s lead-out-of-turn, and that play should proceed as normal from East’s play of the ♥7.