Wis. Stat. § 939.44: Adequate provocation.

(1) In this section:

(a) “Adequate” means sufficient to cause complete lack of self-control in an ordinarily constituted person.

(b) “Provocation” means something which the defendant reasonably believes the intended victim has done which causes the defendant to lack self-control completely at the time of causing death.

(2) Adequate provocation is an affirmative defense only to first-degree intentional homicide and mitigates that offense to 2nd-degree intentional homicide.