Estimating Postmortem Interval
Post –mortem interval which is abbreviated as PMI is defined as the time of elapsing since the death of a person. If the time is not actually known then the medical techniques are used in order to determine that time. Postmortem interval can also be termed as the stage in which a dead body decomposes. Postmortem interval is determined in fundamental step when the death of a person is being investigated especially when the death is in doubt or rather no one witnessed the death. Postmortem estimation is thus defined as that period of time or the length of time experienced between the death of a person and the time of the discovery of corpse. It involves the analysis of the chemical substances which are released after the death of a person and their accumulation in the body.
There are various ways which involve the estimation of the postmortem interval, first, there is the Entomology method which involves the study of insects and the arthropods related. The forensic entomology is used in the death investigation. It provided the objective on estimation of the time of the death of the person and other information concerning the death including the location of the death and the site of the injured parts of the body. (Goff, 243) There is also the entomology of medico legal which involves the use of the insects which are associated with the dead body, it provides information when the normal methods used for estimation cannot. Forensic entomology is applied since the death and beyond 72 hours of time. It is considered to be accurate since it can be applied even after 3 days since the death of the person. (Arnaldos, 57)
The applying of entomology requires factors like the colonization time, time of development and the decomposition of the dead body. The behavior and the ecology of the insect associated with the scene of the death provide the information on how, when and where the crime occurred. Forensic entomology involves the measures for estimation which include the stages of succession which involve the variance of insect species on geographical locations. It has a limitation in that one has to identify the species of insect which is attracted to the remains. Another is the age dependent in the intestinal content, on stage invasion and development of pattern. (Jeffery, 85)
The second method of estimation is based on the energy changes, the change of energy in an organism which is decaying can be monitored using either the temperature of the corpse or the ATP blood level. The method involves the postmortem cooling in which the role of energy metabolism is highly conserved to be used to estimate the various causes of the death. The clothing and the posture of the corpse can cause a drop in temperature. The third method is based on the protein degradation in which protein being a cellular organism component which is found in the body tissues and organs. When the person dies the proteins tend to degrade under the influence of enzymes. According to (Wells, 410) the higher the temperature the longer the frame time and thus the faster the cleavage. This increases the depletion of the muscles cells. Protein degradation which shows a straight line and because of their structure they are probably used for estimation. (Sabucedo, 110) The last method is based on the DNA degradation in which when a person dies the chromosomes in the DNA become smaller over time and the postmortem interval lengthen the chromatin is degraded until there is no formation of a high DNA molecule. DNA is influenced by temperature and the value of pH, The DNA varies in different tissues and muscles thus used in estimation of postmortem interval. The estimation is associated with problems like the weather conditions, the dispersal time, fluctuating temperatures and the effects of photoperiod.
Postmortem interval estimation involves the determination of time which has elapsed after the death of a person. The estimation involves various methods in which some methods were traditionally used while others are more developed. Forensic entomology is defined to be the best method of estimation but it has some limitation regarding the determination of the species o the insect involved and its geographical location at the time of death. Estimation of postmortem interval is an important step in determination of the death time, it helps in identification of the time of the death and information to support the suspects involved in the crime.
Wells, Jeffrey D., et al. “An evaluation of sampling methods used to produce insect growth models for postmortem interval estimation.” International journal of legal medicine 129.2 (2015): 405-410. Wells, t
JEFFREY D. and LYNN R. LaMotte. “Estimating he postmortem interval.” Forensic entomology: the utility of arthropods in legal investigations (2001): 263-85.
Arnaldos, M. I., et al. “Estimation of postmortem interval in real cases based on experimentally obtained entomological evidence.” Forensic Science International 149.1 (2005): 57-65.
Goff, M. Lee. “Problems in estimation of postmortem interval resulting from wrapping of the corpse: a case study from Hawaii.” Journal of Agricultural Entomology 9.4 (1992): 237-243.
Sabucedo, Alberto J., and Kenneth G. Furton. “Estimation of postmortem interval using the protein marker cardiac Troponin I.” Forensic science international 134.1 (2003): 11-16.