Monday, February 20, 2012

Developing Fingerprints on Submerged Weapons Now a Reality

by Andrea Campbell

When new technology comes down the pike, to me, it’s just as interesting as how it came to be—or whose brainchild it is—as is what the science enables us to do. That’s why when I read about this technique for pulling latent fingerprints off of handguns that have been underwater, I had to share it with you as it is on the cusp of becoming mainstream. Some information about the authors and the tests follow.

Kathryn Book for nine years has been a Physical Scientist/Forensic Examiner in the Latent Print Operations Unit at the FBI Laboratory in Quantico. Part of her job is to work with the Bureau’s Evidence Response Team providing latent and human remains processing. The other author and teammate of this plan is James Tullbane, a Supervisory Special Agent on the Technical Dive Team in the Evidence Response Team Unit. Previously he worked as a member of the Underwater Search and Evidence Response Team (USERT) for five years. It’s not surprising that this kind of talent has endeavored to take on a discipline as yet unproven.

The Typical Past
Divers who have recovered materials from water in the capacity of providing evidence for collection, detection, preservation and processing of weapons underwater have basically turned the materials over to the Firearms and Toolmarks Units in order to discover any distinguishing characteristics such as caliber, ammunition and other related tasks. Never had the evidence gone first to the laboratory for latent print processing as it was thought that nothing of significance could be collected in the way of individualistic fingerprints.

Book and Tullbane, however, launched some tests and subsequent studies to see if the possibility of latent print detection and recovery of print evidence could be obtained on handguns that had been submerged in water.

Collection Techniques
The current protocol for collecting handguns within the FBI parameters are to: 1. Photograph the weapon in place, 2. Package the evidence in the found water, and, 3. Submit it to firearms for ballistics testing.

The study and new methodology the authors of these tests took upon themselves found great success: latent prints were developed on weapons tossed into various types of water, well up to 70 days under submersion!

What Are Latents?
In order for fingerprints to be deposited on a surface, they are of two types: Eccrine or Sebaceous. Eccrine (or merocrine gland substances) are the major sweat glands of the human body found in virtually all skin and are fingerprints and is made up of sweat or perspiration that is exuded from the pores of our skin and which highlights the friction ridge patterns on our fingertips. These glands produce a clear, odorless substance consisting primarily of water and NaCl, secretions of the apocrine glands. NaCl is mostly reabsorbed in the duct to reduce salt loss.

Sebaceous prints on the other hand, include fatty acids, lipids, cholesterol and glycerides, including both eccrine secretions and the sebum produced by the sebaceous glands; this is an oily secretion comprised of free fatty acids, wax esters, squalene and more. The most likely method of deposit is when someone touches their nose, hair, skin or other object that contains oils. Now the likelihood of developing the water-based or Eccrine prints is unlikely as they will dissipate in water. Sebaceous prints are less soluable—capable of being dissolved—and the potential for reading them after they have been deposited on a weapon thrown into water is greater.

Difficulty in Processing
Several factors make it difficult to pull prints such as, the surface of the weapon in the way of textured surfaces or a phosphate finish on the weapon, previous oiling or storage of the handgun, and a wiping clean of the gun often provide effective in removing all trace of latents.

Test Set-up
For the testing several natural prints were applied to the weapons along with another print using Lightning Powder’s Latent Print Reference Pad, and all were marked and placed on both sides of the barrel and photographed for reference. Although the tests were conducted in a lab in a controlled environment (e.g. plastic containers), the water used was both fresh and salted with Instant Ocean. Nine trials were done using elapsed time intervals up to 70 days.

Regardless of method of development, processing handguns immediately after removal from water yielded positive results. There were some factors that help to determine the ideal conditions and the things that affect less than prime results are: handguns should be processed immediately, the water temperature if too warm impacts the results; the best results occurred with metal weapons in cold water; and the addition of heat and salt greatly reduces the detection of latent prints.

Obviously further testing and documentation is needed for presentation in court, and evidence proofs in court, but we are very encouraged this will become a mainstay for processing fingerprints from guns thrown into water.


--Book, Mary Kathryn and James Tullbane. "Detection of latent prints on handguns after submersion in water" Adapted from Evidence Technology Magazine, September-October 2011, pages 22-25 and 29.
Image: Stuart Miles /
Gun on dock: Image: Simon Howden /

1 comment:

D. P. Lyle, MD said...

Great post, Andrea.