(1) A person eighteen years of age or older is guilty of the crime of assault of a child in the first degree if the child is under the age of thirteen and the person:

(a) Commits the crime of assault in the first degree, as defined in RCW 9A.36.011, against the child; or

(b) Intentionally assaults the child and either:

(i) Recklessly inflicts great bodily harm; or

(ii) Causes substantial bodily harm, and the person has previously engaged in a pattern or practice either of (A) assaulting the child which has resulted in bodily harm that is greater than transient physical pain or minor temporary marks, or (B) causing the child physical pain or agony that is equivalent to that produced by torture.

(2) Assault of a child in the first degree is a class A felony.