What is the upper hand of using an ALS?

• A. It only works on metal surfaces
• B. Fingerprints can be seen on papers and foils that generally do not yield results
• C. It damages evidence
• D. It makes prints disappear

Answer: (B)

An ALS helps reveal latent fingerprints by exciting residue with light and capturing the resulting fluorescence. The big advantage is that fingerprints can be seen on surfaces like papers and foils where traditional methods often fail to yield results. On these substrates, powders or other visual techniques may not distinguish the print from the background, but the oils and sweat in a fingerprint can fluoresce under the right wavelength, making the print visible for documentation and collection.

ALS isn’t limited to metal; it works across a range of materials, including porous and nonporous surfaces. It is typically non-destructive, so it doesn’t inherently damage evidence, and when used properly it helps preserve prints for lifting. The idea that it would erase prints isn’t accurate, and the claim that it only works on metal is incorrect.