Age estimation of bloodstains using atomic force microscopy in a controlled environment

This study adresses two methods for determining the age of bloodstains, an important challenge in forensic sciences. In the first part, a colour calibration program is written and evaluated to enable quantitative comparison between colorimetric measurements of microscopic digital images that are taken with different cameras. This could enable forensic scientists to create a consistant model for the colour evolution of bloodstains over time. The second and most extensive part of this study evaluates the potential of atomic force microscopy as a method for determining the time since deposition of bloodstains at crime scenes. The effects of temperature and humidity on the Young’s Modulus of red blood cells are analysed and the evolution of the elasticity of red blood cells over time in constant climate conditions is measured. Our experiments show that small and quick humidity changes have significant effect on the Young’s Modulus of the red blood cells. Additionally, the absolute value...Show moreThis study adresses two methods for determining the age of bloodstains, an important challenge in forensic sciences. In the first part, a colour calibration program is written and evaluated to enable quantitative comparison between colorimetric measurements of microscopic digital images that are taken with different cameras. This could enable forensic scientists to create a consistant model for the colour evolution of bloodstains over time. The second and most extensive part of this study evaluates the potential of atomic force microscopy as a method for determining the time since deposition of bloodstains at crime scenes. The effects of temperature and humidity on the Young’s Modulus of red blood cells are analysed and the evolution of the elasticity of red blood cells over time in constant climate conditions is measured. Our experiments show that small and quick humidity changes have significant effect on the Young’s Modulus of the red blood cells. Additionally, the absolute value of the Young’s Moduli varied largely between experiments, which complicates linking certain elasticities to certain times since deposition. This strong climate dependence and large variance in absolute Young’s Moduli make atomic force microscopy a method with little potential when trying to determine the age of bloodstains. Although this is a ”negative” message, it is a very important step forward, as several research groups have attempted to use this method without conclusive results, due to the absence of proper climate control.Show less

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Age estimation of bloodstains using atomic force microscopy in a controlled environment