Comparative analysis of laser polarimetry methods of polycrystalline films of cerebrospinal fluid for post-mortem interval estimation

Abstract

Obtaining the most accurate information about an object during its evaluation is one of the most urgent tasks of current forensic medical examination. That is why the application of new technologies in forensic medical expertise becomes an integral part of the technological support of forensic examination institutions. Purpose: To compare the effectiveness of cerebrospinal fluid polycrystalline films, microscopic images, two-dimensional Stokes-polarimetry, and autofluorescent polarimetry in post-mortem interval estimation over long- and short-term time intervals. Material and methods. The object of the study is cerebrospinal fluid donated from 70 corpses (experimental group) and 20 living persons (control group). Methods used: two-dimensional Stokes-polarimetry, autofluorescent polarimetry. Results: Quantitative characteristics of the cerebrospinal fluid’s polycrystalline films statistical moments allows us to establish relations between them and the duration of the post-mortem interval at a significant time interval. However, this method does not consider the morphology of the film of the cerebrospinal fluid and its coordinate structure. In contrast to this method, fluorescence microscopy considers the biochemical composition of the biological fluid and carries information about the concentration of molecular complexes of proteins, NADH, flavins, porphyrins, etc. In the early post-mortem period, changes in the cerebrospinal fluid begin precisely with changes in the concentration of biochemical compounds, and crystalline changes are secondary, so it can be argued that this method is most effective for diagnosing the progression of the time in the first hours after death. Conclusions: Fluorescent laser polarimetric methods allow accurate estimation of the postmortem interval during the first hours after death. While, the polarization methods is more effective during the long-term periods of time, but has less precision.