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. 2011;6(7):e21845.
doi: 10.1371/journal.pone.0021845. Epub 2011 Jul 15.

Biphasic oxidation of oxy-hemoglobin in bloodstains

Rolf H Bremmer  1 , Daniel M de Bruin, Maarten de Joode, Wybren Jan Buma, Ton G van Leeuwen, Maurice C G Aalders
Affiliations

Biphasic oxidation of oxy-hemoglobin in bloodstains

Rolf H Bremmer et al. PLoS One. 2011.

Abstract

Background: In forensic science, age determination of bloodstains can be crucial in reconstructing crimes. Upon exiting the body, bloodstains transit from bright red to dark brown, which is attributed to oxidation of oxy-hemoglobin (HbO(2)) to met-hemoglobin (met-Hb) and hemichrome (HC). The fractions of HbO(2), met-Hb and HC in a bloodstain can be used for age determination of bloodstains. In this study, we further analyze the conversion of HbO(2) to met-Hb and HC, and determine the effect of temperature and humidity on the conversion rates.

Methodology: The fractions of HbO(2), met-Hb and HC in a bloodstain, as determined by quantitative analysis of optical reflectance spectra (450-800 nm), were measured as function of age, temperature and humidity. Additionally, Optical Coherence Tomography around 1300 nm was used to confirm quantitative spectral analysis approach.

Conclusions: The oxidation rate of HbO(2) in bloodstains is biphasic. At first, the oxidation of HbO(2) is rapid, but slows down after a few hours. These oxidation rates are strongly temperature dependent. However, the oxidation of HbO(2) seems to be independent of humidity, whereas the transition of met-Hb into HC strongly depends on humidity. Knowledge of these decay rates is indispensable for translating laboratory results into forensic practice, and to enable bloodstain age determination on the crime scene.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. OCT image of bloodstain on cotton.
A) Cross-sectional OCT image of cotton fabric with a bloodstain. The left region of interest (red box) shows the position of the bloodstains. The right region of interest (black box) shows a clean spot of cotton fabric. B) Attenuation fits of the OCT signal of bloodstain (red line) and clean cotton (black line).
Figure 2
Figure 2. Diffuse reflectance spectrum of a bloodstain.
The measured reflectance ratio R/R0 of an undiluted bloodstain (BVF = 1) on cotton fabric measured in the spectral range from 450–800 nm. The gray dots depict the bloodstain reflectance and the solid black line represents the multi-component fit.
Figure 3
Figure 3. Validation of fit parameters.
Optically estimated BVF, based on the spectral fits plotted against input BVF based on the mixing whole blood with PBS for eight various dilutions. The solid line represents the line of unity.
Figure 4
Figure 4. Hemoglobin fractions in ageing bloodstains.
Fractions of HbO2, met-Hb and HC in bloodstains (n = 3) monitored for ten days. The amount of HbO2 decrease while met-Hb and HC increases after deposition of the bloodstain. Error bars represent the standard deviation. The blue line shows the biphasic oxidation of [HbO2].
Figure 5
Figure 5. Oxidation parameters vs temperature.
Parameters kf and ks as function of temperature. The fast oxidation (kf) is plotted on the left axis, and slow oxidation (ks) is plotted on the right axis.
Figure 6
Figure 6. Influence of humidity on hemoglobin fraction.
A) HbO2 fraction as function of age of the bloodstain for humidity 20%, 50% and 70%. B) met-Hb fractions as function of age of the bloodstain for humidity 20%, 50% and 70%.
See this image and copyright information in PMC

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