Patent, latent and plastic prints: the three types of fingerprints

"Fingerprint" covers three quite different kinds of mark at a scene. Knowing which you're dealing with decides how you find and recover it.

Patent prints

Patent prints are visible to the naked eye, made when a finger coated in a coloured substance touches a surface — blood, ink, grease, paint or dust. They're photographed in place (with a scale) before any other processing, because the image is the evidence.

Latent prints

Latent prints are invisible — the everyday case. They form from the sweat and oils naturally on the skin and must be developed to be seen, using powders, superglue fuming, chemical reagents or light sources chosen to suit the surface. Most crime-scene fingerprint work is the recovery of latents.

Plastic prints

Plastic prints are three-dimensional impressions pressed into a soft material — putty, wax, fresh paint, chocolate, soap. Because the ridge detail is moulded into the surface, they're recorded by photography (using oblique lighting to throw the ridges into relief) and sometimes casting, rather than dusting.

Why the distinction matters

Each type demands a different first move — photograph the patent print, develop the latent, light and cast the plastic one — and getting the sequence wrong can destroy the mark. Recognising the type on sight is the starting point of every fingerprint recovery.