565.023.  Voluntary manslaughter, penalty — under influence of sudden passion, defendant's burden to inject. — 1.  A person commits the offense of voluntary manslaughter if he or she:

  (1)  Causes the death of another person under circumstances that would constitute murder in the second degree under subdivision (1) of subsection 1 of section 565.021, except that he or she caused the death under the influence of sudden passion arising from adequate cause; or

  (2)  Knowingly assists another in the commission of self-murder.

  2.  The defendant shall have the burden of injecting the issue of influence of sudden passion arising from adequate cause under subdivision (1) of subsection 1 of this section.

  3.  The offense of voluntary manslaughter is a class B felony.