Multivariate Analysis for Estimating the Age of a Bloodstain*

Abstract

Our objective is to provide crime laboratories with a technique for estimating the age of a bloodstain. Toward that goal, we have used multiplexed, real-time RT-PCR (or qPCR) to determine the relative stability of different-sized segments of the same RNA species as well as differences in stability between two different RNAs' change over time in bloodstains. Our results indicate that a multivariate analysis of the changing ratio of the different RNA segments can be used to differentiate between samples of different ages in the defined population. Bloodstains from 29 of 30 donors could be partitioned into different ages using this technique. Although further improvements will be required before this approach can be implemented in crime laboratories, the multivariate analysis holds promise of providing a reliable approach for temporally linking a bloodstain to the commission of a crime or excluding a bloodstain as being irrelevant to the case in question.

Gender-related difference in bloodstain RNA ratio stored under uncontrolled room conditions for 28 days

“…The analysis of variation for the age of the bloodstain produced values of 0.83, for the ratio (18S:b-actin). Anderson et al (2011) found an ANOVA value of 0.93 for the ratio (18S:b-actin), but this may be explained by their temperature-and humidity-controlled experiment .We found that inter-donor variations also showed a linear relationship with age, and the variation seemed to increase with time, with a mean variation between males and females of day 0: 0.0524, and day 28: …”

“…It was also shown that multivariate analysis of different RNA species could be used to differentiate between samples of different ages in the defined population. 8 …”

“…Recent progress in RNA techniques may be used to deduce the possible tissue origin 1e6 and even to determine the bloodstain age. 7,8 This is important because bloodstain age can be very useful in criminal investigations to identify when the crime occurred or to include or exclude an individual as a suspect.…”

“…Anderson et al (2011) chose 0, 6, 30, 90, and 120 days as their study points . Hampson et al chose 0, 1, 5, 15, 30, 45, 60, 75, and 90 days.…”

Métodos para Análise do Tempo desde a Deposição de Manchas de Sangue em Cenas de Crime: Um Diagnóstico Comparativo

“…Porém, até o momento, nenhum dos métodos desenvolvidos e aplicados pôde ser totalmente estabelecido e consolidado na prática forense 6 . Técnicas que incluem a microscopia de força atômica -MFA, ressonância paramagnética eletrônica e degradação do RNA têm sido recentemente exploradas, na tentativa de suprir essa omissão [6][7][8] . De fato, todas estas abordagens confirmam que as propriedades físicas e químicas de manchas de sangue mudam ao longo do tempo.…”