Angular Determination of Toolmarks Using a Computer-Generated Virtual Tool.
A blind study to determine whether virtual toolmarks created using a computer could be used to identify and characterize angle of incidence of physical toolmarks was conducted. Six sequentially manufactured screwdriver tips and one random screwdriver were used to create toolmarks at various angles. An apparatus controlled tool angle. Resultant toolmarks were randomly coded and sent to the researchers, who scanned both tips and toolmarks using an optical profilometer to obtain 3D topography data. Developed software was used to create virtual marks based on the tool topography data. Virtual marks generated at angles from 30 to 85° (5° increments) were compared to physical toolmarks using a statistical algorithm. Twenty of twenty toolmarks were correctly identified by the algorithm. On average, the algorithm misidentified the correct angle of incidence by -6.12°. This study presents the results, their significance, and offers reasons for the average angular misidentification.
Ames Laboratory, Iowa State University, 2220 Hoover Hall, Ames, IA, 50011.
Ryan
R
Spotts
Ames Laboratory, Iowa State University, 2220 Hoover Hall, Ames, IA, 50011.
L Scott
LS
Chumbley
Ames Laboratory, Iowa State University, 2220 Hoover Hall, Ames, IA, 50011.
Laura
L
Ekstrand
Ames Laboratory, Iowa State University, 2220 Hoover Hall, Ames, IA, 50011.
Song
S
Zhang
Illinois State Police, Retired, 3112 Sequoia Dr., Springfield, IL, 62712.
James
J
Kreiser
algorithm; computer simulation; forensic science; statistical comparison; toolmark; virtual toolmark