C.R.S. § 13-90-106: Who may not testify.

(1) The following persons shall not be witnesses:

(a) Persons who are of unsound mind at the time of their production for examination;

(b) (I) Children under ten years of age who appear incapable of receiving just impressions of the facts respecting which they are examined or of relating them truly.

(II) This proscription does not apply to a child under ten years of age, in any civil or criminal proceeding for child abuse, sexual abuse, a sexual offense pursuant to part 4 of article 3 of title 18, C.R.S., or incest, when the child is able to describe or relate in language appropriate for a child of that age the events or facts respecting which the child is examined.