Examination of Firearms Review: 2007 to 2010 - Interpol

3.5 The Examination of Stabbing and Cutting Marks
Many of the studies, conducted in the Review period in the field of identification
and comparison of marks, deal with stabbing, cutting or sawing marks to the
human body. Saville et al (90) studied saw marks on bone using a VP-SEM
(Environmental SEM – ESEM, FEI, The Netherlands) and found three levels of
striations on the kerf walls and floors, each one attributed to a different area of the
cutting saw motion. Two of these striation levels (Types A and B), visible using
stereomicroscopy, are the result of the pushing and pulling of the saw, and they
can provide class characteristics of the saw (its width, the number of teeth per inch
- TPI, etc.). According to these authors, the third group of striae (Type C),
observed here for the first time, are produced by each individual tooth, and may be
used for individualising the specific saw that had left them. The “uniqueness” of
these Type C striations is discussed in the article, and the conclusion drawn by
these authors is that they are unique, based on the results of a limited blind test.
The observation of these Type C striations is only possible by using the ESEM,
due to this instrument high magnification and depth-of-field and its ability to deal
with non-conductive and wet samples.
VP-SEM for the analysis of saw marks in bone was employed also by Freas (91).
This author compared the images obtained using light microscopy with those
obtained using the VP-SEM, and studied the wear-related changes in the kerf wall
and their impact on the interpretation of saw marks in bone. Sequences of 30 cuts
in bone were produced using crosscut saw and hacksaw, revealing patterns of
progressive loss of fine details of kerf wall morphology with increasing saw blade
wear, because of the rounding of sharp points and edges. Nevertheless,
diagnostic kerf wall features used to establish class characteristics persist despite
these wear-related changes. Statistical analysis of wear-related changes, based
on striae width and density, was found to be unsuccessful, suggesting these
patterns are not readily quantifiable. According to this study, despite the scanning
electron microscope’s superior imaging capabilities, it provided only few practical
and methodological gains over the traditional light microscopy.
Marciniak (92) examined the degree of modification of saw-mark characteristics of
dismembered skeletal remains exposed to an outdoor fire of limited duration. The
study material consisted of 36 adult pig hind limbs which had been dismembered
in a fleshed condition. Six different handsaws and six power saws were used, with
three limbs dismembered by each saw type prior to exposure to fire. According to
the results obtained, exposure to fire influences the visibility and identifiability of
the saw-mark striations, but it is still possible to identify the class of saw used on
the basis of the characteristic marks present on the cremated bones.
Bailey and his colleagues (93) studied the kerf marks made by several types of
hand- and mechanical-saws, in order to assess the ability of microscopic
measurements of the kerf mark width to differentiate the tools that produced them.
Their results suggest that this phenomenon may be used as an effective measure
for eliminating some saw blades.
Using the SEM, Lynn and Fairgrieve (94) studied the trauma to mammalian long
bones by axes and hatchets. It was found that striations were present on the
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