A New Perspective in the Estimation of Postmortem Interval (PMI) Based on Vitreous [K+]

Abstract

The relation between the potassium concentration in the vitreous humor, [K+], and the postmortem interval has been studied by several authors. Many formulae are available and they are based on a correlation test and linear regression using the PMI as the independent variable and [K+] as the dependent variable. The estimation of the confidence interval is based on this formulation. However, in forensic work, it is necessary to use [K+] as the independent variable to estimate the PMI. Although all authors have obtained the PMI by direct use of these formulae, it is, nevertheless, an inexact approach, which leads to false estimations. What is required is to change the variables, obtaining a new equation in which [K+] is considered as the independent variable and the PMI as the dependent. The regression line obtained from our data is [K+] = 5.35 + 0.22 PMI, by changing the variables we get PMI = 2.58[K+] − 9.30. When only nonhospital deaths are considered, the results are considerably improved. In this case, we get [K+] = 5.60 + 0.17 PMI and, consequently, PMI = 3.92[K+] − 19.04.

Vitreous Humor: A Short Review on Post-mortem Applications

“…However, the authors do state that most studies have found a useful relationship [20]. Over the years, many scientists have confirmed the existence of this relationship and created different formulas to estimate the time of death with varying accuracy [33][34][35]. Many of the statistical models and equations derived to estimate time since death are based on the assumption that the postmortem increase in vitreous potassium is fairly linear with time and changes at a constant rate [23].…”

Analysis of postmortem metabolic changes in rat kidney cortex using Fourier transform infrared spectroscopy

“…which may presumably cause specific time-dependent changes in metabolism and sub-cellular structures that may be used to determine PMI. Indeed, many sophisticated methods have been used to find reliable markers for the estimation of PMI, including the analysis of potassium concentration in vitreous humor [8][9][10][11] and postmortem protein degradation within different tissues [12,13]. In addition, some researches have been focused on the degradation of nucleic acid including DNA and RNA [14][15][16].…”

Jones-matrix mapping of optically anisotropic fluorophores of molecular biological tissues in the diagnostics of death causes

“…At present time, forensic medicine needs essential renewal of the techniques of DCP estimation. It is related with the fact that existing methods depend on multiple factors of external environment and circumstances of death [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32]. Existing lack of modern, objective techniques of DCP estimation stimulates the search and development of novel techniques for investigation of postmortem changes in human biological tissues and fluids [23].…”