An affirmative defense is essentially a legal justification for having committed a crime; that is, the defendant admits to having committed the crime, but raises a defense that if true would excuse him from criminal liability. Once the defense raises sufficient evidence of an affirmative defense, it is up to the prosecution to disprove that affirmative defense, along with all of the charges, beyond a reasonable doubt.
Should an affirmative defense apply to the facts of your case, it is extremely important that you retain a criminal defense attorney to ensure your defense is properly and timely raised. In Colorado, affirmative defenses must be raised a certain number of days before the trial, so as to provide the prosecution and court with sufficient notice, otherwise they would not be allowed.
Affirmative defenses in Colorado consist of: alibi, self defense, defense of another person, defense of property, duress, choice of evils, and entrapment. Also, voluntary or self induced intoxication can be a defense to some charges. Involuntary intoxication (intoxication that is not self-induced) is a defense to all criminal charges.