Automating the Comparison of Knife Striation Patterns
N. Serdar (TU Delft - Electrical Engineering, Mathematics and Computer Science)
M.B. van Gijzen – Mentor (TU Delft - Electrical Engineering, Mathematics and Computer Science)
D.J.P. Lahaye – Graduation committee member (TU Delft - Electrical Engineering, Mathematics and Computer Science)
K. Herlaar – Mentor (Nederlands Forensisch Instituut (NFI))
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Abstract
When a knife cuts into a material, it creates in it a set of lines, i.e. a striation pattern. Since the striation pattern is individual to each knife, by looking at it, it can be determined (with more or less uncertainty) whether a cut was created by a given knife. This is particularly useful in forensic science for stabbing cases, where it is of interest to know which knife was used for the stabbing. However, the comparison of striation patterns is quite challenging, as they appear different depending on the angle of attack under which they were created, which is generally unknown for the stabbing cases. This project provides a model to compare striation patterns created at different angles of attack, using Dynamic Time Warping. This model was tested with striation patterns created by 6 different knives, and it showed promising results, however some improvements should still be made, which are discussed in the research. Finally, this model provides a solid base to calculate likelihood ratios, which are used to express the certainty that a cut was created by a given knife, as opposed to by another unknown knife.