The Role of DNA Degradation in the Estimation of Post-Mortem Interval: A Systematic Review of the Current Literature

Abstract

The determination of the post-mortal interval (PMI) is an extremely discussed topic in the literature and of deep forensic interest, for which various types of methods have been proposed. The aim of the manuscript is to provide a review of the studies on the post-mortem DNA degradation used for estimating PMI. This review has been performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses and the PRISMA Guidelines. Several analytical techniques have been proposed to analyse the post-mortem DNA degradation in order to use it to estimate the PMI. Studies focused mainly on animal models and on particular tissues. The results have been mixed: while on the one hand literature data in this field have confirmed that in the post-mortem several degradation processes involve nucleic acids, on the other hand some fundamental aspects are still little explored: the influence of ante and post-mortem factors on DNA degradation, the feasibility and applicability of a multiparametric mathematical model that takes into account DNA degradation and the definition of one or more target organs in order to standardize the results on human cases under standard conditions.

MicroRNAs as Useful Tools to Estimate Time Since Death. A Systematic Review of Current Literature

“…Furthermore, most of the data can only be applied effectively for short PMI estimations. Consequently, DNA degradation is considered of limited value in forensic investigations, when used to determine the PMI, as demonstrated in a recent review [70]. Similarly, due to technological advances, researchers are able to use many different methods to study the correlation between protein degradation rate and PMI [75][76][77][78][79].…”

“…Sharma et al employed five mice, collecting brain, heart, lungs, kidneys, pancreas, spleen and liver samples and storing them at 25 • C. The authors focused their attention on AATF mRNA and miRNA-2909; in conclusion was possible to deduce that miR-2909 was stable up to 48 h post-death if the mouse was sacrificed at 8 PM and 12 h post death if the mouse was sacrificed at noon. The authors also concluded that miR-2909 is much more stable to enzymatic degradation then AATF mRNA [41,70].…”

Nuclei DNA Damage Due to Extreme High-Temperature Exposure during Forensic Identification Examination

“…These stages are reflected through color changes that represent the ongoing chemical processes in bones and teeth due to the high temperature exposure. 10,11 The DNA level correlates with the number of nucleated cells in tissues. A bone has nucleated bone cells (osteocytes) of around 20,000-45,000/mm 3 , whereas a tooth has nucleated tooth cells (odontoblast) of around 20,000-26,000/ mm 3 .…”

“…The outer structure of bones and teeth in terms of protection also plays an important role in their resilience against external exposure. 5,10,11 Bone and tooth hardness depends on the amount of inorganic materials contained in the matrix while the strength depends on the organic materials, especially collagen fibers. Teeth enamel consists of 96% inorganic minerals, mainly calcium and phosphorus, and only 4% of organic matters and water.…”

“…GC content or guanine-cytosine bonds have a high level of stability against denaturation factors than the bonds between Adenine and Thymine. 1,3,10 Exposure to extreme high temperatures [1,000°C-1,400°C] significantly [p <0.05] reduces the DNA level of the second costae and molar tooth materials. The STR CODIS and mini-STR loci detection reveals that dental materials might provide adequate protection, where loci are still detected (25%) regardless of high temperature (1,250°C-30').…”