A “Toolbox” for Forensic Engineers

268 Forensic Materials Engineering: Case Studies
Figure 8.7 Lath axe.
Figure 8.8 Fragment of metal removed from eye resting on a 1-mm-square grid.
owned.” He was on the roof using the hammer end to trim brickwork when
he felt something hit his eye. Thinking it was a piece of the brick he rubbed
it and continued working but the pain became so intense he had to stop
working.
The tiny fragment of steel removed from his eye at the hospital, measuring
3.5 mm ¥ 2 mm, is illustrated in Figure 8.8. It has a sharp rim and
the uppermost face exhibits what is referred to as a conchoidal (shell-like)
fracture, characteristic of a piece of hardened steel displaced by a gouging
impact. The other faces resting on the graph paper were worn and bore
features consistent with the outside of this worn hammer head. The confirmatory
test is to place the particle in likely cavities on the suspect tool
and see how well the surface features match the surrounding ones on the
tool. In this instance, not only did the suspect location provide a good
physical fit in the cavity, but it also displays conformity of external contour