Unconsciousness is a complete defense to a criminal charge unless defendant voluntarily induced his or her unconsciousness. Voluntary intoxication includes the taking of an intoxicating drug while knowing of its effects on, in this case, driving.

The most commonly used jury instruction on this defense, CALCRIM 3425, states;

You may consider evidence, if any, of the defendant’s voluntary intoxication only in a limited way. You may consider that evidence only in deciding whether the defendant acted with knowledge that… it could produce an intoxicating effect or willingly assumed the risk of that effect.