The issue of responsibility under sections 18-1-801 to 18-1-804 is an affirmative defense.
C.R.S. § 18-1-805
For other provisions concerning affirmative defenses generally, see §§ 18-1-407 and 18-1-710; for affirmative defenses to particular crimes, see specific criminal provisions in articles 2 to 18 of this title 18.