Comparison of Crime-lite® 82S, Polilight® PL400 and Polilight® PL500 for the detection of semen and saliva stains

Abstract

ABSTRACT Alternative light sources (ALS) are widely employed in forensic investigations for the identification of biological fluids, such as saliva and semen. While metal halide arc lamps are a common light source for many ALS, high intensity light-emitting diode (LED) globes are a more energy efficient alternative. To date, ALS operating with different light sources have not been evaluated against each other, and this study is the first to complete a side-by-side comparison of the arc lamps, Polilight® PL400 (PL400), Polilight® PL500 (PL500) and the LED-based Crime-lite® 82S (blue) (CL82S) for the detection of semen and saliva dilutions on various fabric materials. The absence or presence of fluorescence were scored independently by four experienced item examination scientists to reduce bias. The number of fluorescence stains detected using the CL82S (244 observations) was higher and brighter in intensity compared to those visualized using PL400 and PL500 (183 and 202 observations, respectively). Notably, dilutions of saliva which were not visible under PL400 and PL500 on a range of fabrics were detected under CL82S, which was statistically significant (p < 0.003). Taken together, CL82S is a better screening tool than the PL400 and PL500 for detection of dilute semen and saliva stains on various fabric types.