Use of lead isotopic ratios to discriminate glass samples in forensic science

Abstract

Even though a variety of well-established methods exists for forensic scientists, evaluating the potential of presently un-adopted techniques within the forensic society will always be of high importance. Demand for reduced turnover time is always requested and so are methods that show high ability to discriminate samples that originate from different sources. Glass is common as construction material and in consumer goods. Since glass easily breaks, traces of glass often occur in criminal cases. An obvious assignment for the forensic scientist will be to establish the link between the glass fragments collected on a suspect and the glass from the broken window at the scene of crime. Determination of the refractive index of the seized glass by the oil immersion method is a common method in forensic laboratories. During the last decades, it has been observed that the refractive index has become more similar for glass from different sources. Hence, the evidential value of glass may decrease when refractive index is the single parameter used to determine the origin of glass from the suspect. Consequently, new methods are necessary, and analysis of lead isotope ratios is relevant in this perspective. This work establishes a novel method for analysis of lead isotope ratios in order to differentiate glass from different sources. To perform such analysis by Multi-Collector Inductive Coupled Plasma Mass Spectrometry, an analytical protocol is developed. The statistical method of Tukey's Honestly Significant Difference Test for multiple comparisons of samples appeared helpful in a forensic context.