Advertisement

Researchers have shown that the striation pattern impressed in costal cartilage during the creation of a cut mark is an adequate representation of the tool’s cutting edge and can be used to identify class and individual characteristics of the tool. Therefore, the current method of classifying a blade type is based on the presence/absence and regularity of striations.

In light of the increased attention levied on expert testimony in the courts, this study was designed to validate the current method through independent testing and measurement of the potential error rate. The goals were to evaluate: 1) the repeatability of the impressed striations by the blade into the cut costal cartilage; and 2) the probability of correctly classifying the blade type based on the striation pattern observed on the cut surface.

The results of the study indicate a very high potential error rate when analyzing cut marks in costal cartilage using the current generally accepted method – 66 percent of the cut surfaces were misclassified. However, the accuracy of the analysis improved when using another well-established approach, the classification tree method.  

The initial classification tree built on all the variables collected during the study resulted in a misclassification rate of just 12 percent. A second classification tree was constructed on all variables, except the variables that reflected the dimensions of the cut surface. When using the classification tree method and including the mean interstriation distance increased the accuracy of the analysis; however, the error rate was still at nearly 50 percent.

Read the report.

Source: NIJ

Advertisement
Advertisement