AK bullet (7.62 × 39 mm) holes on 1-mm sheet metal: A forensic-related study in aid of bullet trajectory reconstruction.

Bullet holes play a major role in the trajectory determination of fired bullets, potentially suggesting where the shots were fired from. Few methods are currently employed to estimate the angles of incidence of fired bullets using bullet holes. The literature has stressed that knowledge about the impact behavior of the specific bullet-substrate interfaces, including the most viable method for estimating the angle of incidence of that combination, requires empirical testing to enable successful analysis. The perforating bullet hole characteristics of AK bullets fired into 1-mm sheet metal over a range of angles of incidence have been documented in this study to aid bullet trajectory determination. A strong inverse relationship has been demonstrated between particular impact mark dimensions and the angles of incidence, revealing the possibility of using these dimensions to predict the angles of incidence for AK bullets perforating 1-mm sheet metal in actual crime scenes. This study has further confirmed the existence of a recently reported phenomenon for impacts related to this projectile-substrate combination, the "double-headed impact mark," and relationships with the angles of incidence of fired AK bullets. While suggesting an alternative and confirmative new method to understand the angles of incidence of fired AK bullets in 1-mm sheet metal using measured bullet defects, the study highlights a complex deviation phenomenon and a potential error that could occur when determining bullet trajectories using probing, stringing, or laser methods for the impact conditions described.