Posted on Wednesday, February 11, 2009 - 04:46 pm:

Q:  How long do fingerprints last on evidence?
A:  Fingerprints on paper, cardboard and unfinished wood can last for up to forty years (per actual casework histories) unless exposed to water (and contaminate transfer prints can even then sometimes persist). Fingerprints on non-porous surfaces such as plastic, metal and glass can last for many years if not exposed to water and if left undisturbed.

Q: Can a Fingerprint Expert determine if latent prints are "fresh" versus old?
A: Estimates about the age of latent prints are unreliable when the experts guessing have no idea what was on the fingers that touched a surface. Latent prints that develop "quickly, strongly or dark" are not necessarily consistent with having been "recently" deposited. Unless scientific analysis of latent print residue on evidence was completed before processing with powder or chemicals to visualize latent prints (which is an analysis seldom performed because latent prints tend to be invisible until processed), then the nature of the latent print residue deposited by the fingers or palms cannot be known (whether it was fried chicken oil, grease, natural secretions from the fingers, etc.). Circumstantial evidence such as information that an item was cleaned thoroughly with glass cleaner, soap and water, etc., could date latent prints on the item as not being older than the last thorough cleaning.