Measurement of substance P and met-enkephalin in the serum of violent death victims.

Very often the allocation of putative damages for wrongful death and the determination of aggravating factors in the sentencing of an individual convicted of homicide by a jury is based on a subjective determination of the amount of pain suffered by the victim. This study was designed to determine whether the quantitative determination of peptides involved in nociception and inflammation offer the potential to provide an objective basis for an assessment of pain prior to death. Two peptides. substance P and met-enkephalin, were quantitated using radioimmunoassay (RIA) in the serum of 131 autopsy subjects. Cases were selected that presented decedents who underwent a violent death resulting in extensive trauma to tissue. Only decedents with no known prior clinical manifestation and no indication of prior drug use were selected. Of 131 cases selected, 59 died from blunt trauma deaths, 47 from gunshot deaths, and 25 from stabbing deaths. Cases were selected without regard to whether the death was accidental, or by homicide or suicide. Values from cases having similar incident-death time intervals were pooled and then compared. Results show that an observable pattern exists between the concentrations of substance P and met-enkephalin and the incident-death time interval. Data showed that the concentrations of substance P and met-enkephalin vary with the incident-death time interval. The amount of serum substance P initially increases with increasing incident-death time interval but begins to decrease at longer incident-death time intervals. In contrast, the serum concentration of met-enkephalin continues to show increased concentration as the incident-death time intervals become greater. The Kruskal-Wallis test was performed to determine the level of significance of the variation in both peptide concentrations within four consecutive time intervals. Variation in substance P concentration was statistically significant in all comparisons performed with 0.01 being the lowest level of significance of any four consecutive groups tested. Conversely, intervals encompassing incident-death time intervals of 1-2 hours to 5-10 days did not demonstrate significant variation in met-enkephalin concentration. However, groups with smaller and larger time intervals than the nonsignificant groups did show statistical variation. Although owing to a number of variables, a direct correlation between peptide concentrations and the level of pain may not be possible, the results of the study indicate that a presumption of antemortem pain may be possible with future study.