Comparison of methods for visualizing blood on dark surfaces.

Difficulties can arise when screening dark casework items for blood, a poor contrast between blood and the background can mean stains are not always evident. Typical indirect searching methods can be time consuming and may result in potentially important bloodstains being missed. Luminol, fluorescein, hydrogen peroxide, ultraviolet light and infrared photography were tested in an effort to find a rapid and efficient blood search tool for direct application to dark surfaces. Methods were compared in their sensitivity, specificity, ability to work on various surface types and their effect on DNA extraction and typing. Along with experimental results, the ease of use, costs and the health and safety considerations were also compared. Hydrogen peroxide was determined to be the most effective method. However, where blood was likely to be dilute, luminol was proposed due its greater sensitivity.