A meta-analytic review of the weapon focus effect.

This meta-analytic review examined 19 tests of the weapon focus effect—the hypothesis that the presence of a weapon during commission of a crime will negatively affect an eyewitness's ability to later identify the perpetrator. A significant overall difference between weapon-present and weaponabsent conditions was demonstrated, with weapon presence leading to reduced identification accuracy. Overall, the size of the effect was small (.13) for the dependent measure of lineup identification and moderate (.55) for feature accuracy. Discussion focuses on those factors that appear to mediate and facilitate the weapon focus effect.