The search was conducted on five electronic data banks: Scopus (“”n = 29), Science Direct (n = 174), PubMed (n = 26), Embase (n = 28), and Springer (n = 274) using the BOOLEAN system to obtain journals for a total number of 535. From 535 journals, 77 were automatically excluded by the system for journals published under 2012, and 74 were duplicated, bringing the total to 384. The automatic screening was carried out to exclude 208 journals that were not research journals, bringing the total journal to 176. Title and abstract screening was carried out to look for the journal that matched the inclusion criteria, as many as 139 journals, so the number of journals becomes 37. Thirty-seven journals were read entirely, and 19 journals did not meet the criteria or did not answer PICO, so the final journals that will be reviewed are 18. The PRISMA flow chart results are in Fig. 1.

Synthesized data include the first author’s name, year of publication, study location, sample, and the number of samples, Treatment (euthanasia technique, temperature storage, cause of death), tissue source used, RNA extraction technique, amplification technique, miRNA target, results, conclusions, and research limitations (Table 1).

From 18 journals, research conducted in several countries such as Iran (n = 1) [4], Mexico (n = 1) [6], South Korea (n = 3) [19, 24, 25], China (9) [9, 21, 26,27,28,29,30,31,32], Saudi Arabia (n = 1) [33], UK (n = 1) [34], Italy (n = 1) [35], Spain (n = 1) [15]. Of the 18 journals, nine researches used animals (rats/mice) as a sample [4, 6, 21, 25, 27, 29,30,31, 33]. Seven researchers used the human body as samples [15, 19, 24, 26, 32, 34, 35], research that used animals and human body as a sample in as many as two journals [9, 28].

Tissue source used in this study are varied: liver [4, 9, 27, 32], skeletal muscle [6, 27, 32], blood [24, 35], bone [19], heart [9, 21, 26, 27, 31, 32], skin [32, 33], saliva [34], semen [34], brain [21, 25, 29, 32], lungs [28], vitreous humor [15, 35], lymph [30], and kidneys [32].

The materials used to perform the RNA extraction used are different. They use QIAzol lysis Reagent (Cat. No.79306, Qiagen, USA) [4], Trizol™ reagent [6], Trizol™ reagent (ThermoFisher Scientific, Waltham, MA, USA) [19], miRNeasy serum/plasma kit (Qiagen, Hilden, Germany) [24, 35], Trizol™ reagent (Invitrogen, USA) [19, 25,26,27, 29,30,31,32], TriR reagent (Sigma-Aldrich, Gillingham, UK) [34], Takara, Japan, RNAiso Plus (Takara, Japan) [9, 21], Trizol reagent (Life Technologies, USA) [25], AmbionR mirVana™ miRNA Isolation Kit (Ambion, Austin, TX) [15, 33]. All studies used amplification techniques to quantify miRNA expression levels by RT-qPCR.

From 18 journals, 8 journals found results in the form of changes in miRNA expression levels after an interval of death [4, 6, 15, 19, 21, 25, 26, 33]. One journal showed a negative correlation between miRNA expression levels and post-mortem interval, namely miR-16 and let-7e [19]. The results of other studies say that further research is needed for miR-3381-3p because it has great potential. In addition, 10 journals found that miRNA expression level values were stable throughout the post-mortem interval [9, 24, 27,28,29,30,31,32, 34, 35].

In addition, several different treatments were carried out. Derakhshanf et al gave different treatment when preparing the sample. They use CO2 gas and ketamine/xylazine injection [4]. Kim SY et al. gave different treatment by taking blood samples from different places such as peripheral blood, heart blood, and coronary sinus blood with the results significantly different miRNA expression levels [24]. Han L et al. took samples of corpses with different causes of death, like poisoning, craniocerebral injury, mechanical asphyxia, and hemorrhagic shock. miR-3185 had increased expression levels in samples that died because of mechanical asphyxia [26]. Corradini B. et al. took samples by differentiating the time of death of the samples that are during the day and at night with the results of differences in expression levels in samples that died during the day and at night [35]. Yu S et al. conducted a study by differentiating the sample immersion media, namely, plain water and salt water. Regulation of miR-706 increased in plain water, while in salt water, its regulation has decreased [25]. Lv Y et al. carried out different treatments on the samples which were stored at 25 °C ± 2 and 4 °C ± 2. The results showed that miRNA has a stable expression in both treatments [30]. Odriozola A et al. conducted different samples in the form of time of death, which are during the day and at night. The results showed stable expression levels in both the samples that died during the day and at night [15]. Zhang H et al. took samples with different causes of death, namely, head injury, hemorrhagic shock, mechanical asphyxia, and sudden cardiac disease [32].