An evaluation of luminol formulations and their effect on DNA profiling

Luminol is a presumptive test reagent used for the location of latent bloodstains. Various formulations are used by different forensic practitioners and commercial products are also widely available. There is little concurrence between authors with regards to the sensitivity limits of luminol which can vary significantly depending upon the substrate. We evaluated the sensitivity and stability of five different luminol formulations on a range of blood dilutions. All formulations showed an overall decrease in performance over 24 h though the effect was more gradual on a non-porous surface compared to porous. We found that BlueStar® Magnum showed the greatest sensitivity compared to other formulations and detected 50 μl of 1/100,000 blood dilutions on both porous and non-porous surfaces. Two formulations of luminol were selected based on the result of the sensitivity and stability study and were assessed for their impact on the DNA profiling process. There was a statistically significant improvement in DNA profile peak area from luminol-treated samples when compared to control samples of neat blood stains. However, at the weaker blood dilution of 1/1,000, the difference between control and luminol-treated samples was dependent on the substrate type with porous (fabric) samples showing a significant difference and non-porous (tile) swabbed samples requiring further work to conclusively ascertain the effect.