What is the purpose of luminescence tests in bloodstain detection and what is a common caveat?

• A. Reveal latent bloodstains under UV or blue light; caveat: can react with certain cleaners and metals causing false signals.
• B. Used to positively identify the blood type.
• C. Determine the DNA sequence of the stain.
• D. Quantify the amount of blood.

Answer: (A)

Luminescence tests reveal latent bloodstains by producing light when the sample’s heme iron catalyzes the oxidation of a reagent like luminol, so traces of blood that aren’t visible can be seen under low light. A common caveat is that these tests are not perfectly specific: certain cleaners with oxidizing agents or some metal-containing substances can also produce luminescent signals, leading to false positives. Because of that, positive luminescent results are typically followed by confirmatory blood-specific tests to verify the presence of blood.