(1) As used in this article 12, unless the context otherwise requires:

(a) "Adult" means any person eighteen years of age or older.

(a.3) "Ballistic knife" means any knife that has a blade which is forcefully projected from the handle by means of a spring-loaded device or explosive charge.

(a.5) "Blackjack" includes any billy, sand club, sandbag, or other hand-operated striking weapon consisting, at the striking end, of an encased piece of lead or other heavy substance and, at the handle end, a strap or springy shaft which increases the force of impact.

(b) "Bomb" means any explosive or incendiary device or molotov cocktail as defined in section 9-7-103, C.R.S., or any chemical device which causes or can cause an explosion, which is not specifically designed for lawful and legitimate use in the hands of its possessor.

(b.5) "Bureau" means the Colorado bureau of investigation created in section 24-33.5-401, C.R.S.

(c) "Firearm silencer" means any instrument, attachment, weapon, or appliance for causing the firing of any gun, revolver, pistol, or other firearm to be silent or intended to lessen or muffle the noise of the firing of any such weapon.

(d) "Gas gun" means a device designed for projecting gas-filled projectiles which release their contents after having been projected from the device and includes projectiles designed for use in such a device.

(e) Repealed.

(e.5) "Handgun" means a pistol, revolver, or other firearm of any description, loaded or unloaded, from which any shot, bullet, or other missile can be discharged, the length of the barrel of which, not including any revolving, detachable, or magazine breech, does not exceed twelve inches.

(e.7) "Juvenile" means any person under the age of eighteen years.

(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.

(g) "Machine gun" means any firearm, whatever its size and usual designation, that shoots automatically more than one shot, without manual reloading, by a single function of the trigger.

(h) "Short rifle" means a rifle having a barrel less than sixteen inches long or an overall length of less than twenty-six inches.

(i) "Short shotgun" means a shotgun having a barrel or barrels less than eighteen inches long or an overall length of less than twenty-six inches.

(i.5) "Stun gun" means a device capable of temporarily immobilizing a person by the infliction of an electrical charge.

(j) Repealed.

(2) It shall be an affirmative defense to any provision of this article that the act was committed by a peace officer in the lawful discharge of his duties.