Kevin has made a ruling on BGG that this isnt possible.

However, when I played Louis, someone played a dark card on me when it wasnt my turn. This is the card which is played when Louis is placing a lead. This can only be done when it isnt Louis' turn cant it?

Not necessarily, there are some effects that let you move a lead on your turn, such as lead symbols on conspiracy tiles or the special rules of the "Last Call at Roxie's" murder sheet.

However, I agree with you, it would make sense if this particular card could be played anytime Louis is moving a lead (even if it is not his turn).

Loius places a lead -> Louis has an advantage.

Dark Card played -> puts advantage back into balance.

Nowehere it states that dark cards HAVE to be played on the other player's turn.

Paul Grogan said:

I am not sure what Kevin said but my assumtpion is NOT that you can only play cards on someone's turn but that you can only play cards in reaction to another player's moves.

So if Louis does something while it isn't his turn, he is still doing something and for that you can play a card. I thinkt he ruling was intended to say you can't play a dark card on someone if they haven't done something - which is typically what would happen when it is not their turn.

Quote from KevinW on BGG:

"You can only play a detective's Dark cards during that player's turn. Otherwise, that opens things up to weird things happening, like a player losing Time when he doesn't have any. "

Need this clarified in the upcoming FAQ - face it, there is bound to be some!

One part of Louis´s "Sara" plot allows him to place the leads that he follows himself. So I think it is only just there is a dark card which has a disadvantages for him in this area.

About playing dark cards at other times than in a given player´s turn: as written in rules, the cards take precedence... so this one can probably be played ANYTIME Louis moves a lead (the fact is if this would be stated on the card explicitly, things would be easier).