Breakaway Spur
Definition
A chip or spur of cortical bone on the exit face of a saw kerf, produced when the final tooth exits the bone; its direction indicates the direction of the saw stroke.
- Location
- Exit face of a saw kerf
- Cause
- Final tooth exiting the bone
- Forensic use
- Indicates direction of saw stroke
- Context
- Sharp-force and saw-mark trauma analysis
Common questions
How does a breakaway spur help distinguish a saw from a chop wound?+
A breakaway spur is a feature specific to the repetitive back-and-forth cutting action of a saw exiting bone; a single chop wound from an axe or similar blade does not produce this exit-face chipping pattern, so its presence supports saw dismemberment over a single-blow injury.
Can a breakaway spur alone identify the type of saw used?+
By itself it mainly indicates stroke direction; identifying saw type, such as blade set pattern or tooth pitch, usually relies on additional kerf-wall striations and the kerf floor shape examined together with the spur, not the spur in isolation.
Related terms
- Class Characteristics
- Features deliberately or systematically imparted to a group of items by design or manufacture, such as the calibre of a bullet, the...
- False-Start Kerf
- A short, incomplete saw mark adjacent to the main kerf, produced when the cutter repositioned the saw after an unsatisfactory initial entry...
- Hinge Fracture
- A curved crack running from the deepest point of a chop kerf to the opposite cortex, producing a free-floating triangular fragment; characteristic...
- Incised Wound
- A wound produced by a sharp-edged implement. Margins are clean, without contusion or bridging. Depth is less than length in a classic...
- Kerf
- The groove or channel cut into bone by a sharp implement; its width, wall angle, floor texture, and profile are the primary...
- Kerf Wall Squareness
- The angle of the kerf walls relative to the bone surface; square walls indicate a stable, perpendicular saw stroke; canted walls indicate...
- Residual Tooth Marks
- Individual tooth impressions in the floor of an incomplete saw kerf, allowing direct measurement of tooth geometry and TPI when the saw...
- Tooth Set
- The lateral bending of saw teeth alternately left and right of the blade body, producing a kerf wider than the blade itself;...
- TPI (Teeth per Inch)
- The number of teeth on a saw blade per inch of blade length; determines the spacing of striation marks on the kerf...