If you ever get questioned by the law.. do as in the title!
The Law knows perfectly well how to deal with those who admit and those who deny - playing ignorant throws a wrench into the system.
Ofc you won't be able to do this all the way, but give ground sloooooowly, never say anything other than "I don't know, I can't recall.."
Obviously never admit to anything even the most obvious("law: did it rain that day? - you: I can't recall", "law: where you breathing at that moment? - you: I can't recall"). And deny only as a last resort - because if you do deny than you will put your self on the spot to come up with an alibi or other excuse, you will paint your self into a corner and the law-officer if very well trained into forcing a confession from you if he get's you there.
If you start denying than obvious questions will come up like "so if you wheren't at the crime scene, where where you?" or "if you did not do this than why are you so nervous?" or "you say you did not do this, but we know you did 'something else'" etc.
Play dumb, play ignorant and ASK for a LAWYER.. but never trust your lawyer either!
And if you get into a situation where you think they got you, make like a stone and STOP TALKING!