Estimation of the postmortem interval by chemical means.

The literature is reviewed regarding estimation of the postmortem interval (PMI) by chemical analysis of cadaver fluids. The most useful measurements on blood and CSF are amino nitrogen, nonprotein nitrogen, ammonia, creatine, and inorganic phosphate; these have some value in the early PMI. Probably the single most accurate determination is the potassium content of the vitreous humor, which shows a linear rise with time in the interval 12-100 hours postmortem. The rate of vitreous potassium rise is fairly independent of environmental influence. Other determinations that may prove valuable include the potassium content of the aqueous humor and the ammonia and magnesium content of the vitreous. Although no single measurement gives a completely reliable estimate of the PMI, combinations of chemical determinations can be useful adjuncts in cases of unwitnessed death.