Abstract: It is suggested that combined index is an available approach for the aim atelevating the probability of distinguishing between death and survival whenpoisoning in the work of clinic and forensic toxicology.DDVP is an exampleof it.Probability of coincidence(P_c)is used as a combined index which can beexpressed as:P_c=P_1×P_2×……P_nIn P,three parameters—blood DDVP concentration,blood cholinesterase andspasmodic bronchiarctia in the lung—are used in it.As an example,after cal-culating the survival rates from a series of equations in the text,the probabi-lity of survival can be elevated from 0.05 and 0.23 of each single parameter to0.0006 of combined index P.It means that the probability of death can beelevated from 95% and 77% to 99.94%.It is concluded that P.is an effectiveindex in clinic and forensic toxicology.