54 Cutting tools leave two types of characteristics, indi- vidual and class, that can be used to analyze tool marks. Individual characteristics are random imperfections along the leading edge of the cutting tool that produce striations on a substrate; therefore, these striations can be used to match a cutting tool to a speciﬁc tool mark. Class char- acteristics include similarities that can place the tool in a category or eliminate it from a group [6–8]. For example, a saw blade that is 6.350 mm in thickness could be elimi- nated from a cut mark that is 3.175 mm in width. More- over, in any form of physical comparative analysis, class characteristics are examined ﬁrst to determine if they are the same or similar. If a tool can be eliminated based on a difference in class characteristics, it is not necessary to search for individual characteristics. However, if the class characteristics are the same or similar, a physical match or elimination can be achieved based on the agreement or disagreement of individual characteristics [9]. When saws are used to cut bone, they sometimes leave marks known as false starts. False starts occur when the saw blade comes into contact with bone brieﬂy, removes some of the bone but then stops, skips or restarts in a new position usually close to the initial cut and continues to cut the bone [10]. The characteristic examined in this study was the kerf width of a saw cut into compact bone. The kerf mark widths were measured to determine which pos- sible saw blade could be eliminated based on the kerf width. Methods Ten sections of bovine bone were cut into *22.86 cm by *5.08 cm sized pieces and used as a substrate to collect kerf marks from ﬁve human-powered and ﬁve mechanical- powered saws. The human-powered saws included: a hand saw, hack saw, meat saw, bow saw and molding cut-off saw. The mechanical-powered saws included: a recipro- cating saw, circular saw, cut-off saw, portable band saw, and jig saw. Of the mechanical-powered saws, the circular saw, cut-off saw and portable band saw used cutting blades with a rotating motion. The reciprocating saw and jig saw used cutting blades with a reciprocating motion. Kerf marks were produced on the diaphyseal sections by sawing into the cortical bone with each of the saws. The depth of each saw cut was approximately the thickness of the compact bone. Figures 1, 3, 5, 7, 9, 11, 13, 15, 17, and 19 illustrate the saw blades used and Figs. 2, 4, 6, 8, 10, 12, 14, 16, 18, and 20 illustrate the kerf for each of the blades respectively. Dial calipers were used to measure the thickness of each saw blade. Before recording measurements, steps were taken to ensure the dial calipers were operating properly. 123 Forensic Sci Med Pathol (2011) 7:53–62 Fig. 1 Portable band saw blade Fig. 2 Portable band saw blade kerf Fig. 3 Hack saw blade First, the dial caliper jaws were closed and the pointer setting was at ‘‘0.’’ Second, using the thumbwheel, the dial caliper jaws were opened to the maximum distance and