Relevant statues:
18-12-101:
(f) "Knife" means any dagger, dirk, knife, or stiletto with a blade over three and one-half inches in length, or any other dangerous instrument capable of inflicting cutting, stabbing, or tearing wounds, but does not include a hunting or fishing knife carried for sports use. The issue that a knife is a hunting or fishing knife must be raised as an affirmative defense.
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Defendant's intent to use an object as a weapon is not established by the object's appearance alone, even if the appearance demonstrates that its primary use is as a weapon; this test does not follow Gross and is contrary to the plain language of the concealed weapons statute. A.P.E. v. People, 20 P.3d 1179 (Colo. 2001).
18-12-105
The definition of "knife" in subsection (1)(f) of this section is sufficiently specific to give fair warning of the proscribed conduct and is therefore constitutional. In applying the definition under section 18-12-108,
the prosecution must prove that one of the intended uses of the instrument by the defendant was as a weapon. People v. Gross, 830 P.2d 933 (Colo. 1992).
Defendant could not be convicted of carrying a concealed weapon without the prosecution proving that defendant intended to use this short-bladed knife as a weapon. While the characteristics of an instrument may be an important factor in determining the intended purpose of an instrument, the language of the concealed weapons statute and established precedent establishes that a knife's design does not, by itself, prove that the person carrying it intended to use it as a weapon. A.P.E. v. People, 20 P.3d 1179 (Colo. 2001).