Abstract
Time of death (TOD) determination is crucial in criminal cases. The method used to determine the TOD so far is only based on the state of the corpse found, therefore a new method is needed to improve the accuracy of the TOD determination. This study aims to determine the TOD based on a new method, namely the formation of blood rings and RNA degradation. Blood is commonly found in crime scenes. Blood consists of liquid part that is plasma and cellular part consisting of erythrocytes, leukocyte, and thrombocytes. The composition of blood as a liquid that contains dissolved solids makes the drops of dried blood forming “coffee ring effect”, which is a ring-like form on the perimeter of a blood drop. Coffee ring effect is used as an indicator of time by looking at the thickness of the ring formed from the perimeter of the blood drop to the middle which increases with time. RNA degradation was observed using Peptidylprolyl isomerase A (PPIA) gene. The PPIA gene is found in leukocyte and is used to see the degradation of RNA per 30 minutes period using the RT-PCR and qPCR methods. Degradation was observed by comparing the cycle threshold (ct) value of the standard curve with the ct value of the samples per unit time. TOD could be determined by the percentage of the blood ring thickness up until 120th minutes, and by observing the degradation of RNA until the 60th minute, after that the RNA had completely degraded.
Highlights
Timeliness in determining the time of death (TOD) is crucial to determine a person's involvement based on the suitability of the alibi possessed with the TOD
Blood consists of a fluid part called plasma, and a cellular part consisting of red blood cells, white blood cells and platelets (Kulstein, 2018)
The composition of blood as a liquid containing dissolved solids makes drops of blood fluid can be used as an indicator of time in determining TOD based on the coffee ring effect
Summary
Timeliness in determining the time of death (TOD) is crucial to determine a person's involvement based on the suitability of the alibi possessed with the TOD. The composition of blood as a liquid containing dissolved solids makes drops of blood fluid can be used as an indicator of time in determining TOD based on the coffee ring effect. The research shows the evaporation process that occurs in blood drops, which are liquids with dissolved substances. The ABO blood grouping system is determined based on 4 molecules determining blood group, namely: 1) D-galactose; 2) Nacetylgalactosamine; 3) Nacetylglucosamine; and 4) L-fucose (Murray, 2009) These molecules attach to red blood cells and produce antigens which determine blood group. The ABO blood grouping system has different structure in molecular and antigens, so it is necessary to look at its effect in the formation of blood rings. A genetic approach to determine the TOD is by looking at the RNA degradation in the blood drops found. Quantitative PCR has fluorescent labelling that shows numbers of amplified genetic material after accumulated in the reaction in real time after each amplification cycle has finished (Bustin, 2009)
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