ASIS International (ASIS) Professional Certified Investigator Practice Exam

Which chemical method will produce white fingerprints on dark surfaces?

1. Ninhydrin

2. Cyanoacrylate fuming

3. Iodine fuming

4. Pulverized chalk

The correct answer is: Cyanoacrylate fuming

The method that produces white fingerprints on dark surfaces is cyanoacrylate fuming, commonly known as superglue fuming. This technique is effective for enhancing latent fingerprints because the cyanoacrylate vapor adheres to the fatty acids and proteins present in the fingerprint residue. When the vapor comes into contact with the fingerprint, it polymerizes and forms a solid, white substance that outlines the fingerprint in a high-contrast manner against dark surfaces, thereby making the prints easily visible. This method is particularly advantageous because it can be applied to a variety of surfaces, including plastics, metals, and glass. Other methods listed, such as ninhydrin, iodine fuming, and pulverized chalk, have different mechanisms and results. Ninhydrin typically develops purple prints on paper and porous surfaces, iodine fuming creates brownish prints that can fade, and pulverized chalk is often used to highlight prints but does not produce a permanent result like cyanoacrylate does. Thus, cyanoacrylate fuming is the preferred choice for obtaining durable and visible white fingerprints on dark backgrounds.