The consequences of potentially differing distributions of the refractive indices of glass fragments from control and recovered sources

The effect of re-annealing on the distribution of refractive index in a windscreen and a windowpane

“…The windowpanes are usually cut from ready flat sheet of glass and then toughened, whereas windscreens are usually made with the use of one or two, usually metal, forms. Flat sheet of glass is heated to the temperature at which the glass softens and then it is put into the form, sometimes pressed with other form, and then cut and However, the deviations are small and the RI distribution could be approximated by normal distribution, whereas it is not the case with recovered glass [10]. The observed distributions are approximately symmetric and will converge rapidly to normality according to Central Limit Theorem [11].…”

Application of false discovery rate procedure to pairwise comparisons of refractive index of glass fragments

“…Results of comparisons, based not only on statistical tests but also range tests, confidence intervals and likelihood ratio method, could be greatly affected by the different RI of float surfaces and therefore false conclusion about common origin of compared glass fragments could be made. Examination of float glass made by Zoro et al [4] and confirmed by Newton et al [5] show that there are significant differences between both the mean and variance of refractive index of float surface and mean and variance of bulk or antifloat surface. Refractive index of a float surface could also affect the distributions of RI in compered objects such that the assumption of normal distributions used in statistical testing and confidence interval testing is invalid.…”

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

“…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.…”