For the purposes of this chapter:
1. A killing is “felonious” if it is committed without legal excuse or justification.
2. A killing is “intentional” if it is caused by or occurs during the commission of any act which involves a degree of culpability that is greater than criminal negligence.
3. Insanity or diminished capacity shall be deemed not to be a legal excuse or justification and must not be considered in determining whether a killing is felonious or intentional.