A person in possession or control of any building, realty, or other premises, or a person who is licensed or privileged to be thereon, is justified in using reasonable and appropriate physical force upon another person when and to the extent that it is reasonably necessary to prevent or terminate what he reasonably believes to be the commission or attempted commission of an unlawful trespass by the other person in or upon the building, realty, or premises. However, he may use deadly force only in defense of himself or another as described in section 18-1-704, or when he reasonably believes it necessary to prevent what he reasonably believes to be an attempt by the trespasser to commit first degree arson.
Source: L. 71: R&RE, p. 409, 1. C.R.S. 1963: 40-1-805.
Cross references: For first degree arson, see 18-4-102.
Law reviews. For article, "Self-Defense in Colorado", see 24 Colo. Law. 2717 (1995). For article, "POWPO and Gun Rights After Carbajal", see 44 Colo. Law. 31 (Sept. 2015).
Common-law doctrine of retreat not applicable. Where the jury was told that though the defendant was in his place of business, and was in no way the aggressor, a deadly and unprovoked assault was made upon him by one armed with a loaded pistol, he was under duty to flee unless it was more dangerous to retreat than to fight, it was held a pernicious application of the common-law doctrine of retreat to the wall long since abrogated in this jurisdiction. Enyart v. People, 67 Colo. 434, 180 P. 722 (1919) (decided under R.S. 08, 1634).
One cannot instantly kill in defense of property. While a man may use all reasonable and necessary force to defend his real and personal estate, of which he is in the actual possession, against another who comes to dispossess him without right, he cannot instantly carry his defense to the extent of killing the aggressor. If no other way is open, he must yield and get himself righted by resort to the law. Bush v. People, 10 Colo. 566, 16 P. 290 (1887) (decided under G. S. 721).
This section is not, by its terms, inapplicable to unlawful entries where the trespassers happen to be police officers. People v. Lutz, 762 P.2d 715 (Colo. App. 1988).