Post Number: 200
|Posted on Thursday, November 02, 2006 - 06:02 am: ||
Relatively soon after latent prints are deposited (minutes to hours depending on environmental factors including relative humidity, temperature and air flow) from the natural secretions of eccrine glands covering the friction ridges of fingers/palms or soles/toes, the water content of the residue evaporates (eccrine glands secrete no oils), leaving behind the many solids which are the target of most latent print development techniques. Unless the surface is severely damaged by the heat of the fire (e.g., charred black), latent prints will often survive. It is common in fires for there to be latent prints on partially-burnt papers, especially near the charred edges where the heat has caused the latent print residue to darken.
Crime scene technicians should be aware that the smoke of a fire may develop latent prints in a manner similar to latent print powders, with excellent quality impressions revealed beneath layers of soot. The layers of soot may be gradually removed to reveal latent prints by (depending on the nature of the soot) brushing with a fingerprint brush, rinsing gently with water, or sequential lifting of soot layers using latent print lifting tape (or other lift materials). The "flame technique" for developing latent prints has been discussed in forensic literature for over 30 years (see Hot Prints - THE USE OF FLAME IN THE DEVELOPMENT OF LATENT PRINTS, Identification News, Feb 1975, page 11).
If a person has touched their face, hair, etc., and picked-up sebaceous contaminates, they could then deposit sebaceous contaminated prints. There is also a slight "flow" of sebum from the dorsal surface of the hands to palmar surface, but it provides much less residue than the constantly replenished eccrine gland secretions. Of course, many other contaminates (oil from popcorn or fried chicken, engine oil, grease, dirt, paint, lipstick, body fluids, etc.) may be present on fingers/palms... thus the sequential order in which latent print processing techniques occur. Latent Print Examiners lack ESP and, in the absence of visible friction ridge detail, make no assumptions about what may or may not have been present on fingers/palms touching a surface.
(Message edited by member on November 02, 2006)
Sean English (mocktrailer)
Post Number: 1
|Posted on Wednesday, November 01, 2006 - 03:54 pm: ||
I am currently involved in a Mock Trial program for the state of New Mexico. I am a high school student in need of a little information from the pro's. My question is "If there was a house fire would all fingerprints be erased in the heat?" A friend of mine said that most fingerprnts are erased anywhere from 95* F to 110*F and above but those are the generally accepted temperature for fingerprint's to start to break down. I also read where fingerprints are mostly made of water (on this forum), but what about the oil? Does the oil disappear also and at what temperatures? Thanks so much for any and all information pertaining to this I appriciate the help.