NCJ Number
187600
Journal
Journal of Forensic Sciences Volume: 46 Issue: 2 Dated: March 2001 Pages: 209-214
Date Published
March 2001
Length
6 pages
Annotation
This paper draws up a new formula for determining the postmortem interval (PMI) based on the increase of potassium concentration ([K+]) in the vitreous humor.
Abstract
The relationship between the [K+] and the PMI has been studied by several authors. Many formulae are available, and they are based on a correlation test and linear regression that uses 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 that leads to false estimations. What is required is to change the variables so as to obtain a new equation in which [K+] is considered the independent variable and the PMI is the dependent variable. The research reported in this article studied 201 samples from 164 deceased subjects (in 37 cases samples from both eyes were obtained simultaneously) received for autopsy in the Institute of Legal Medicine of the University of Santiago de Compostela, Spain. A total of 201 samples from 127 men and 37 women were used. The regression line obtained from the data in the current research is [K+] = 5.35 + 0.22 PMI. By changing the variables, the equation becomes PMI = 2.58[K+] - 9.30. When only nonhospital deaths were considered, the results were considerably improved. In this case, [K+] = 5.60 + 0.17 PMI; consequently, PMI = 3.92[K+] - 19.04. 5 tables, 3 figures, and 17 references