Untitled

Abstract

Sheet glass samples were collected from diŠerent sources of 3 domestic manufacturers in Japan. Refractive index (RI) was measured for the evaluation of source discrimination capability of them. Variation of RI value within a sheet glass, which was calculated from RI measurement for the fragments taken from 5 diŠerent position in each of 4 sheet glass samples, was 1.9×10 by standard deviation at maximum. A pair of sheet glass samples was considered to be distinguishable when they oŠered diŠerence in RI value more than 2.8×10 -4 , which corresponded to the range of ±2s in the intra sample variation. Number of distinguishable pair was 793 of 861 for all the possible pairs among 42 samples collected, 555 of 587 for those from diŠerent manufacturers, 161 of 173 for those from diŠerent plants of a same manufacturer, 49 of 55 for those from diŠerent furnaces of a same plant and manufacturer, which can be considered to provide satisfactorily good discrimination capability for the forensic discrimination of glass fragments. Only 28 of 46 pairs were distinguishable when they originated from a same furnace, plant and manufacturer. Among the characteristic of sheet glass, such as ‰oat or gured, color and thickness, color was found to have remarkable relationship with RI value. Compared within the same manufacturer, colored glass oŠered higher RI values than colorless ones except for 4 samples. Although they were from an identical origin, 24 of 27 pairs with diŠerent color could be discriminated from each other.

Forensic Discrimination of Sheet Glass by a Refractive-Index Measurement and Elemental Analysis with Synchrotron Radiation X-ray Fluorescence Spectrometry

“…It is reported that the variation of RI within a sheet glass across different sampling positions is smaller than 0.0002, which was calculated as the maximum range of the mean ± 2SD. 9,14 Compared with the inner-sample variation, RI for the 11 sheet glasses occurred over a wide range from 1.5186 to 1.5204. Discrimination of these glasses was performed as follows.…”

“…[1][2][3] The forensic discrimination of glass fragments has been carried out by comparing the color and thickness, 4 observing the original surface under an interference microscope, 5 and measuring the refractive index (RI) and density. [6][7][8][9][10] However, a comparison of the optical and morphological characteristics can be applied only to sufficiently large fragments, which are rarely found in actual cases. Improvements in quality control during the manufacturing of glass have made the variation for RI of glass smaller, resulting in a reduced discrimination capability by the comparison of RI.…”

Forensic Discrimination of Sheet Glass Exposed to High Temperature by the Determination of Trace Impurities Using ICP-MS

“…The measurement of RI was repeated 5 times for each sample using different fragments. 10 Analysis of trace elements by ICP-MS. Each piece of a glass sample was washed with ethanol and water before use. After being dried in an oven, this piece was crushed into smaller fragments of appropriate size (approximately 2 mg or smaller) with an agate mortar.…”

“…It is reported that variation of RI within a pane of sheet glass is less than 0.0002. 8,10 Two pieces of glass fragments are considered to originate from different sources when they provide a larger difference in RI than this decision range of identity. The difference in RI between the heated and non-heated glasses obtained by this experiment is approximately from 6 to 7 times larger than the decision range of identity.…”

“…If tiny glass fragments found on the clothes of a suspect can be proved to originate from the broken window glass, they can be valuable physical evidence to associate the suspect with the crime. [1][2][3][4][5][6] The forensic glass comparison mentioned above has been conducted by measuring the refractive index (RI) [5][6][7][8][9][10][11][12][13][14] and conducting an analysis of the elemental compositions using procedures such as X-ray fluorescence spectrometry (XRF), 6,8,12,[15][16][17][18][19][20][21][22] inductively coupled plasma atomic emission spectrometry (ICP-AES) 8,15,[23][24][25] and mass spectrometry (ICP-MS). 5,6,9,12,18,[26][27][28][29] An RI measurement can be applied to a glass fragment smaller than 0.1 mm in a maximum width without its destruction.…”