Determination of Bloodstain Age by UV Visible Integrating Sphere Reflection Spectrum

Abstract

To establish a method for rapid identification of bloodstain age. Under laboratory conditions （20 ℃, 25 ℃ and 30 ℃）, an integrating sphere ISR-240A was used as a reflection accessory on an UV-2450 UV-vis spectrophotometer, and a standard white board of BaSO₄ was used as reference, the reflection spectrums of bloodstain from human ears' venous blood were measured at regular intervals. The reflection radios R₅₄₁ and R₅₇₇ at a specific wavelength were collected and the value of R₅₄₁/R₅₇₇ was calculated. The linear fitting and regression analysis were done by SPSS 17.0. The results of regression analysis showed that R² of the ratios of bloodstain age to UV visible reflectivity in specific wavelengths were larger than 0.8 within 8 hours and under certain circumstances. The regression equation was established. The bloodstain age had significant correlation with the value of R₅₄₁/R₅₇₇. The method of inspection is simple, rapid and nondestructive with a good reliability, and can be used to identify the bloodstain age within 8 hours elapsed-time standards under laboratory conditions.