Blood is the most commonly observed known contaminant found at scenes of crime, which is possibly because, when present even in small quantities, it is easily seen as it strongly absorbs light throughout the visible spectrum. However, when present in minute amounts or in the dark, patterned, or multicolored confusing backgrounds, the blood may require enhancement to make it more useful for evidential purposes. Additionally, proof that a stain is actually blood rather than an innocuous substance may be important in assessing guilt or innocence and may even be a matter of life or death in some cases.