______ is a chemical method of detecting latent blood.

• A. Luminol
• B. Luminal
• C. Hemastix
• D. Fluorescein

Answer: (B)

Detecting latent blood chemically relies on a reaction that makes invisible stains glow. Luminol is a chemical reagent that, in the presence of hydrogen peroxide and a catalyst such as the iron in blood, undergoes chemiluminescence and emits a blue glow. When sprayed on a suspected area, any trace blood will light up briefly, revealing stains that aren’t visible to the naked eye and may be hidden or cleaned. This makes luminol a standard tool for locating blood traces at crime scenes. It isn’t perfectly specific to human blood and can produce false positives with other peroxidase-containing substances, and it can affect DNA analysis if used before sampling. The other options aren’t used for latent blood detection: Luminal is a barbiturate, Hemastix tests for blood in urine, and Fluorescein is a fluorescent dye used in other contexts.