Latent Prints on Submerged Handguns
Written by Mary Kathryn Book and James Tullbane   

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Detection of Latent Prints on Handguns After Submersion in Water

RECENTLY, the authors of this article worked to determine the potential for recovering latent prints from handguns that had been submerged in water. The purpose of this research is to provide guidance for the FBI’s Underwater Search and Evidence Response Team (USERT), for evidence recovery divers in the public-safety field, and for latent-print examiners involved in the collection, detection, preservation, and processing of weapons after submersion in water.

Currently, no studies have been published pertaining specifically to latent-print detection on handguns that have been submerged. This study was performed by the authors from a field and laboratory perspective to explore the possibility of latent-print detection and recovery on handguns after submersion in water. The study is intended to serve as a guide for divers as well as latent-print examiners in establishing protocols when such items are recovered as evidence.

Current Protocols

Within the FBI, handguns are located and collected by divers in the field. They are photographed in place, secured, and packaged in the water in which they are found. They are then submitted to the Laboratory for processing. In many instances, the handguns are submitted directly to the Firearms and Toolmarks Unit (FTU) without being processed for latent prints. This research was performed by the authors to determine if the hand-guns could be processed for latent prints immediately after removal from the water.

Background

This study tested the likelihood of detecting latent prints using various time trials, substrates, water types, and temperatures. The following hypothesis was formulated:

Length of time in water +
higher water temperature =
drastic reduction in the detection of latent prints on handguns

Latent prints are deposited when the friction-ridge structure of the skin comes into contact with a suitable surface. Pores must exude perspiration or another transfer medium must be present for a print to be left behind. Latent-print residue is typically either eccrine or sebaceous. Eccrine, or sweat prints, are largely made up of water. The remaining constituents include organic compounds and inorganic salts. Sebaceous prints include fatty acids, lipids, cholesterol, and glycerides deposited when the finger comes into contact with a surface. Sebaceous prints are often left when an individual touches hair, skin, or another object that contains a coating of oil.

Because the majority of latent-print makeup is water, submerged evidence has a greater likelihood of prints dissipating prior to initial processing. Sebaceous prints, however, are less soluble; therefore, there is potential for detection and development of latent prints after items have been submerged in water.

Handguns in particular have a difficult substrate for successful development and detection of viable latent prints. Several factors contribute to low latent-print recovery rates, including phosphate finishes, textured surfaces, oiling, and the storage of guns and wiping them clean after use. With the addition of water to the equation, the probability of detecting latent prints suitable for comparison lessens greatly.

Initial Set-Up

Because there was very little frame of reference for time that a latent print will last on a submerged weapon, the time trials were originally set up from one to 21 days. Since the results were still positive at 21 days, this research includes nine time trials that take the study up to 70 days.

Seventy-two handguns were provided by the FTU. For the initial set-up, specimens were wiped clean with a cloth. Six fingerprints were placed on the weapon.

The shape of the handgun as well as surface type determined the placement of prints. Prints were “spiked” with natural and artificial sebaceous matrices. One natural female print, one natural male print, and one print using Lightning Powder’s Latent Print Reference Pad for sebaceous oil secretions were placed on each side of the barrel. Print placement was marked on the handguns. The guns were photographed once after latent prints were deposited (prior to submersion in water) and once after final processing was complete.

Since the purpose of this study focused on how long a latent print could survive on a submerged handgun, all handguns were placed in a container within the Laboratory. The survivability under ideal conditions was tested prior to adding variables to the equation. A controlled environment was necessary to set a baseline for preliminary results. In order to establish a controlled environment, handguns were submerged in plastic containers filled with water rather than in actual bodies of water. Fresh-water was collected from a nearby lake. Tap water with Instant Ocean was utilized to create a saltwater environment. The containers were labeled accordingly with a naming system to positively identify samples.

Trials

Nine trials were completed. Trial 1 through Trial 9 represent time elapsed after initial submersion of the handguns. Print processing occurred on days 1, 2, 7, 14, 21, 28, 42, 56, and 70.

The study introduced several variables to include handgun material, water type, water temperature, and the development method.

Eight handguns per trial were processed to include all variables. Table 1 represents the process followed.

Trial 2 through Trial 9 repeated the same process. The designation of one through nine represents time in water. In total, 72 weapons over a 70-day period were processed (Figure 3).

After each trial, the condition of the water was observed and document-ed at initial removal of the handgun. A visual examination was conducted upon removal from water and in some instances prints were detected visually prior to processing. The guns were then processed immediately with either small particle reagent or WetPrint, dried with a heat gun, processed in a superglue fuming chamber, and photo-graphed. One of the variables tested was processing technique. Is it better to process while wet or allow the handgun to dry prior to processing?

Results

This is the first published study specifically pertaining to the detection of latent prints on handguns after submersion in water. Latent prints were developed up to 70 days. The results indicate that regardless of method of development, processing handguns immediately after removal from water yields positive results (Table 2).

In cold-water trials over a 70-day period, 40 fingerprints were developed on metal handguns in saltwater, 39 prints were developed on metal handguns in freshwater, 12 prints were developed on polymer handguns in freshwater, and 11 were developed on polymer handguns in saltwater.

In warm-water trials over a 70-day period, 34 fingerprints were developed on metal handguns in freshwater, 27 prints were developed on metal handguns in saltwater, 17 prints were developed on polymer handguns in saltwater, and 11 were developed on polymer handguns in freshwater.

Discussion

Results from this study have potential to act as a guide to divers as well as lab examiners in determining if latent-print examinations are feasible. How long should a diver proceed with caution? At what point should the firearm be submitted directly to a firearms unit instead of being examined for latent prints? These results are considered preliminary because additional variables need to be introduced. That being said, these results provide a guideline for latent-print detection in ideal conditions.

Prior to this research, there was no indication as to how long a latent print could survive or if it was necessary for a diver to use caution when handling a recovered firearm. The results indicate that in ideal conditions, it is possible to develop a latent print on a submerged weapon up to 70 days. There were several other findings:

• Processing handguns immediately after removal from water increases print detection; the method of development was insignificant.
• An increase in water temperature negatively impacts latent-print detection and development.
• The data indicates that the best results occurred with metal weapons in cold freshwater.
• The addition of heat and salt drastically reduces the detection of latent prints.

Consistently, polymer handguns produced the fewest latent prints. Poly-mer handguns in saltwater yielded more latent prints than in freshwater. During visual examination, it appeared that the saltwater caused a reaction with the latent-print residue. Although a layer of visible rust coated the hand-gun, it did not fully preclude latent-print detection and development.

Metal was more receptive to prints than polymers. That result is consistent with other studies concerning latent prints on firearms or similar substrates.

Several types of metal handguns were utilized in this study. Although metal, the guns were made of various materials. The type of metal seemed to play a large role in latent-print detection. Stainless-steel handguns yielded the best results.

Prior to this study, it was not known how long a latent print would remain on a handgun after submersion in water. Although many additional variables need to be introduced, it is apparent that in ideal conditions, a sebaceous latent print may be recoverable from a submerged firearm up to 70 days after its deposition. This study should provide sufficient preliminary results for a dive team to adjust protocols. Results suggest that crime-scene personnel recovering submerged weapons should exercise caution to ensure any recoverable impressions are not inadvertently compromised in the recovery process. It may also assist latent-print examiners in adopting processing procedures when weapons enter the laboratory. Regardless of processing technique, processing the handguns immediately after removal from water yields the best results.

The final trial in this study produced positive results. While this information concludes this phase of the research, future research endeavors include the addition of a stirring device to imitate moving water, adding silt or sand to the containers, placing handguns in actual bodies of water, and longer time trials.

Preliminary studies only tested up to 70 days. At the completion of this portion of the study, the basic question still remains: Exactly how long will a latent print survive on a submerged firearm?

About the Authors

Mary Kathryn Book is a Physical Scientist/Forensic Examiner in the Latent Print Operations Unit at the FBI Laboratory in Quantico, Virginia. She has served in this position for approximately nine years. For the past five years, she has worked closely with the Bureau’s Evidence Response Teams by providing latent-specific and human-remains processing training. She is also an active member of the FBI’s Disaster Squad.

James Tullbane is a Supervisory Special Agent on the Technical Dive Team in the Evidence Response Team Unit. As an FBI Agent for more than seven years, he has been involved in counterterrorism and criminal investigations. He was a member of the Under-water Search and Evidence Response Team (USERT) for five years and served as the senior team leader for four of the five years.

The authors would like to give special thanks to the following:
• SSA Kevin J. Horn, ERTU USERT Program Manager
• Michael Williams, Forensic Imaging Unit Latent Photographer
• FBI Laboratory’s Latent Print Units and Firearms and Toolmarks Unit

Disclaimer
Names of commercial manufacturers are provided in this article for identification purposes only. Inclusion does not imply endorsement by the Federal Bureau of Investigation.

 
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