|Posted on Monday, May 28, 2001 - 02:00 pm: ||
Sensitivity (for faint deposits) and contrast (from the background color) are two or the most important factors when deciding which processing technique to use on a surface suspected of bearing latent prints.
Superglue fuming guidance is given here and here.
Superglue fuming in a crime laboratory is normally followed-up with luminescent dye stain processing and examination under a laser or alternate light source.
If you do not follow-up with luminescent dye-staining to "tag" faint deposits, you can miss up to 50% of the identifiable latent prints which have been developed with superglue fumes but lack sufficient contrast from the background to ever be seen… even after "dusting" with a contrasting color powder.
The following anecdote from 17 years ago illustrates the problem of only dusting with powder after superglue fuming:
In July, 1984 I was visiting a friend in Martinez, Georgia when Georgia Bureau of Investigation (GBI) Special Agent James G. “Jimmy” Tarvin told me of the absence of physical evidence in the investigation of a high school student’s brutal murder a year earlier. Plastic garbage bags wrapped around the victim’s head and feet had been processed by the GBI Laboratory in Atlanta, resulting in several latent fingerprints that belonged to personnel present at the crime scene, but none from the suspect in the case. In an ideal world with unlimited time and resources, best possible non-porous surface examination would also probably incorporate reflected ultra-violet imaging system (RUVIS) and/or vacuum metal deposition. In the not-so-ideal world most police agencies operate in, a more typical and very effective flow chart might be:
Tarvin asked for a favor. Having heard of the professed “miracles” of laser examination, he asked me to re-examine the plastic bags as a last resort for positively linking the suspect with the murder. At least a fifty percent chance existed of finding any additional latent fingerprints because the GBI had already properly processed the bags with cyanoacrylate ester (“superglue”) fumes and fingerprint dusting powder, techniques overall more successful than (inherent luminescence) laser examination. I was midway though 30 days’ active duty as a reserve Special Agent with the US Army Crime Lab (located at Fort Gillem, GA) and I agreed to help (the GBI Laboratory had no laser in July 1984).
Rhodamine 6G in a methanol solution was applied to the plastic bags and then rinsed off with clean methanol to remove the dye stain from all possible background areas. The rhodamine dye “tags” minute (often invisible) remnants of cyanoacrylate-developed latent fingerprint ridge detail and causes it to luminesce under laser excitation (diffused to resemble a monochromatic flashlight). In this case approximately 10 watts average power argon-ion all-lines illumination was used by me to reveal several identifiable latent fingerprint that had been left on the plastic bags, but had not been detected by superglue fuming and dusting with contrasting colored powder.
One laser-detected latent print from the garbage bags belonged to the suspect. The suspect in the 1983 murder was one of the victim’s high school teachers at the time of her death and he had since moved from Georgia to Texas where he was teaching school. In March, 1986 the suspect entered a guilty plea to murder… all resulting from following-up superglue fuming (and dusting) with dye staining and laser examination.
Excerpted from "The Forensic Laser Widens Its Role" , by Edward R. German, published in PHOTONICS SPECTRA / THE INTERNATIONAL JOURNAL OF OPTICS, ELECTRO-OPTICS, LASERS, FIBER OPTICS AND IMAGING, July, 1986.
- white light visual exam
- inherent luminescence exam
- cyanoacrylate fuming
- white light visual exam
– luminescent dye staining
– luminescence exam
– “dusting” with contrasting color powder
– “rubbing” with contrasting color powder
(with photography of any considerably improved prints of value between each step)
|Posted on Monday, May 28, 2001 - 08:09 am: ||
The advantages of supergluing and item before dusting it with black powder, are two fold. The superglue keeps the print stable for dusting and you can make numerous lifts off the same print without destroying the latent. I superglued a persons drivers license on a homicide case, where the suspect had removed the victims license from his pocket, in the process of looking for money. The license produced both the suspects right index and the right thumb print on each side of the license. The more I lifted the print, the cleaner the latent showed. It seems that with each lift, the trash in the latent was removed, making the print even more visible. Hope this helps.
melcon s. lapina
|Posted on Tuesday, November 21, 2000 - 08:50 pm: ||
Hello! I am a graduate of Criminology and presently working on my thesis about the comparison of the effectiveness of the superglue fuming method and dusting method of developing latent fingeprints on nonporous surfaces.
I welcome any opinion concerning which of these methods is effective.