Assessing the time since death (TSD) is a foremost routine task forensic medical experts perform daily. Establishing the postmortem interval is extremely important in investigating criminal cases, in the reconstruction of events, and in establishing the circumstances that preceded the death. Accurate determination of the TSD can significantly contribute to the investigation, setting a time frame on which efforts and resources can be directed. This problem has a priority in connection with the legal significance in the planning and conduct of operational and investigative measures. However, despite the rapid development of science and the large number of annually proposed modern methods of determining the TSD, for a forensic medical expert, this task remains quite challenging, both at the time of examination of the corpse at the scene of death and later, during the autopsy, especially in cases of suspected poisoning by different groups of poisons. After all, most of the techniques used in practice are based on the visualization of macro- and microscopic changes in the body after death. However, the speed of their development can be influenced by such factors as air temperature, humidity and precipitation, features, and condition of the body on the eve of death, the cause of its occurrence, trauma, intoxication, etc.
At the same time, it is noteworthy that there is almost no information in the sources of world literature about specific morphological changes in biological tissue (BT) in various pathological conditions, namely ethanol (E) and carbon monoxide (CO) poisoning. All of the above encourages the search for new diagnostic methods for establishing TSD in A and CO poisoning for use in forensic practice. A set of laser polarimetric techniques (LPT) developed through cross-sectoral integration of forensic medicine and physics solves many of the above problems, allows rapid diagnostics, and has objectivity, speed, independence, sufficient accuracy, and reproducibility of results.
A study of histological sections of the brain, myocardium, adrenal glands, liver, and polycrystalline blood films (PBF) of deceased persons of both sexes aged 19 to 76 years with a previously known time of death ranging from 1 to 40 hours was conducted. To carry out the study, the corpses of those who died due to coronary heart disease (CHD) (control group) and E and CO poisoning with a known time of death were selected.
For the first time, the possibility of statistically reliable (p1; p2; <0.05) differentiation of death cases was established by calculating the statistical moments of higher orders characterizing the distributions of the value of the crystallization parameter (CP) of microscopic images of histological sections of the brain, myocardium, adrenal glands, liver, and human blood, demonstrated a good level of accuracy of differential diagnosis of cases of E and CO poisoning by differential Mueller-matrix polarimetric microscopy with algorithmic reproduction of the linearly and circularly birefringent polycrystalline component of BT.
The possibility of statistically reliable (p1; p2; p1,2<0.05) forensic differentiation of the cause of death was established, and operational characteristics of the diagnostic power of the method of polarization tomography of LB and CB of optically active molecular complexes were determined - sensitivity, specificity and balanced accuracy correspond to satisfactory (myocardium), good (brain, liver) and excellent (adrenal glands, blood) levels.
For the first time, the forensic effectiveness of statistically reliable (p1; p2; p1,2<0.05) differentiation of cases of E and CO poisoning by differential Mueller-matrix polarimetric microscopy with algorithmic reproduction of LB and CB fluctuations of the polycrystalline component of histological sections of the brain, myocardium, and adrenal glands was established, human liver and PBF. An excellent (average, dispersion, asymmetry → 93-97%) level of accuracy of differential forensic medical diagnosis of cases of E and CO poisoning was determined.
For the first time, the effectiveness of Stokes-polarimetric microscopy, azimuthal-invariant Mueller-matrix mapping, polarization-phase, and diffuse differential Mueller-matrix tomography of the polycrystalline structure of layers of biological preparations for accurate determination of time since death is demonstrated. A set of forensic medical criteria for determining the time since death by monitoring the temporal changes in the set of statistical moments of the 1st - 4th order is determined. Based on this, for the first time, the accuracy of determining the age of death of 0.5 h in the interval up to 60 hours by Mueller-matrix algorithmic reproduction of maps of fluctuations of birefringence of optically anisotropic component of biological drugs (sensitivity range for brain tissue - up to 24 h, blood - 30 h, liver - 48 hours, adrenal glands - 48 hours, myocardium - 60 hours).
