What is the preferred liquid for fingerprinting?

• A. Soap and water
• B. Rubbing alcohol only
• C. Distilled water only
• D. Soap and water, however rubbing alcohol may be substituted

Answer: (D)

The idea being tested is which cleaning liquid best prepares a surface for fingerprint development without disturbing the fingerprint residue. Soap and water is the best choice because it effectively removes surface oils and contaminants that can hide or blur a print, while being gentle enough not to disrupt the fingerprint residue itself. This makes it versatile for a wide range of surfaces and situations, allowing powders or chemical developers to adhere and reveal the print clearly. Distilled water alone doesn’t remove oils well enough, so it’s not as effective. Rubbing alcohol can be useful on some materials, especially where water isn’t available, but it dries quickly and can cause prints to smear or be damaged on certain surfaces. Therefore, soap and water is preferred, with rubbing alcohol as a substitute when water can’t be used.