"Negative Results" Evidence and Testimony
Successful gun crime prosecution often depends on the prosecution's ability to educate jury members on the meaning of the police report notation: "no prints recovered." Jurors must understand that an inability to recover fingerprints does not establish conclusively whether or not a defendant touched or fired a particular firearm. Thanks to dramatized television gun cases, some jurors have come to expect that every time a firearm is handled, identifiable telltale prints are left behind to prove or disprove a defendant's guilt. Ironically, prosecutors have sometimes presented eyewitness testimony that a particular defendant fired a weapon, but have been unable to present corresponding testimony regarding viable prints. Unfortunately, in reality it is rare that usable prints are lifted from recovered firearms. To survive defense challenges, prosecutors should, through expert witness or trained officer testimony, help jurors understand what has been termed "negative results testimony," or the circumstances that lead to an absence of prints despite all evidence that a firearm has been fired.
How A Fingerprint is Created
The inner surface skin of our hands, fingers and foot soles is corrugated, and contains raised skin known as friction ridges. The configuration of these ridges is unique to each individual. The perspiration excreted from fingers and palms is primarily water and a small amount of solid matter containing chemicals found in natural secretions, blood and contaminants. The perspiration clings to the individual's friction ridges and is transferred upon contact with a smooth surface. This transferred perspiration is a key factor in determining whether a usable latent print can be recovered. Several conditions must be present before a clear print can be retrieved from a firearm. To lift a print, there must be sufficient unevaporated perspiration for the chemical developing or processing agent to adhere and produce a clear print. In warm weather, too much perspiration may cause distorted prints to be transferred; in cold weather, less perspiration is produced, often resulting in an inadequate medium for print transfer. The friction ridges must exude some perspiration for grease, oil, or other matter to collect--otherwise no print will be left on the touched object.
Factors Affecting Recovery of Prints
Prosecutors should he prepared to present testimony regarding the fragile condition of fingerprints as well as the many factors affecting recoverability, including, for example, how the firearm was handled, where it was deposited, atmospheric and environmental conditions, and the nature of the firearm's surface and finish. There may be sufficient fragmentary print detail to indicate that the firearm was handled but insufficient prints to make a comparison or identification. Prosecutors should be prepared, if appropriate, to present expert testimony that despite state-of-the-art equipment, identifiable latent prints frequently are not recoverable, and, further, that a lack of fingerprint evidence does not prove the defendant did not handle a firearm.
Environmental Factors. Seasonal temperature, air, and water all impact the condition and ability to obtain prints of value. If the firearm has been fired in rapid succession, portions of the firearm may become hot, causing rapid evaporation of hand perspiration and affecting contact salts and amino acid residues. On a humid day, a firearm may collect moisture on its surface, causing the latent deposits to wash away; conversely, on a hot day with low humidity, portions of the user's perspiration may evaporate rapidly. If a firearm is left out in the rain, the oily portions of the latent print may be washed away or smeared beyond recovery. Other water-based substances coming in contact with the firearm may degrade the quality or recoverability of usable prints. For example, dew acts like rain and combines with residual perspiration; it may even form a surface barrier on the firearm itself, preventing print residue from collecting to allow for detection. In addition, a firearm may be thrown into rapidly moving water, thus destroying viable prints.
Handling Factors. On occasion, a fleeing offender will shove a firearm into a pocket or waistband and smear his or her prints. Repeated impact against another surface also may smudge or wear away critical portions of a print. If the firearm was recovered from the defendant's waistband, it is helpful for the report to indicate whether the defendant was wearing a sweat suit or other soft, loose-fitting clothing to explain, in part, why portions of the print may have worn off. Some defendants destroy clean prints when they wipe down a firearm after using it. If a firearm is well kept, it frequently will be slightly oily, which increases the potential for smeared prints if the user holds it tightly when firing or if there is a significant jolt when it is fired.
If a firearm is recovered from under a car seat, the act of pushing the firearm against the floor carpet may have destroyed or obliterated prints. Throwing a firearm from a moving car may cause it to come in contact with other surfaces (e.g., a dusty dirt road, leaves, or other vegetation), thus altering the prints.
Surface and Coating Factors. Another roadblock for prosecutors in recovering good prints is the surface condition of the firearm and the type of finish applied to the firearm's metal surfaces. Typically, firearms contain both smooth and textured surfaces. Firearms manufactured with smooth surfaces are better for recovering latent prints. Textured surfaces, which are most commonly used on grips or stocks, are not suitable for recovering prints. Some firearms are manufactured using textured polymer surfaces, which are not suitable for transferring prints. Special coatings on firearms, e.g., to prevent rust or lubricate, also can make it difficult to recover prints. Some firearms manufacturers advertise that their firearms provide "an excellent resistance to fingerprints." It may be appropriate for the testifying witness to describe or present firearms advertising material to the jury.
Conclusion
"Negative results" or "no prints" need not be a death knell for gun crime prosecutors. Through careful case presentation, expert testimony can help to prevent jury speculation and enhance a just resolution to the firearms case. For additional information on fingerprints and processing techniques, see: U.S. Department of Justice, Federal Bureau of investigation, Laboratory Division's Handbook of Forensic Services and Processing Guide for Developing Latent Prints, or contact Superintendent of Documents at P.O. Box 371954, Pittsburgh, PA, 15250-7954 or by calling 202-512-1800.
APRI Trainings
The final session of APRI's "Hitting the Mark: Implementing & Maintaining Community Gun Violence Prosecution Initiatives" was conducted November 3-5, 2003, concluding this series of prosecutor trainings in support of Project Safe Neighborhoods (PSN). A total of 500 prosecutors attended these programs in Baltimore, MD; Los Angeles, CA; Chicago, IL; and Boca Raton, FL. A new series of PSN prosecutor trainings is being developed for 2004. This new series will target effective strategies to prosecute gun cases, continue support of PSN programs, and refine PSN "best practices" to enhance developing, as well as on-going, gun violence prosecution programs.
Specialized Workshops
Michigan State University has developed an advanced workshop to build on the skills developed through Strategic Problem Solving trainings that were previously provided to PSN Task Forces. Designed specifically for PSN Coordinators and Research Partners, the new workshop series will focus on issues in project implementation, coordination, and research analysis. Current plans call for an additional workshop dealing with rural PSN issues to be offered in February or March 2004.
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