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Pattern and Impression Evidence 

Pattern and impression evidence includes any markings produced when one object comes into contact with another object, such as fingerprints, shoeprints, toolmarks, and tire treads. It also includes pattern analysis, such as is used when evaluating handwriting, typewriting, and writing instruments.

  • Bloodstains
  • Firearms and Toolmarks
  • Latent Prints/Tenprints
  • Ondontology (Bitemarks)
  • Questioned Documents
  • Shoeprints and Tire Treads

Specific Projects

Expert Working Group on Human Factors in Latent Print Analysis
Although courts have accepted latent fingerprint evidence for the past century, several high-profile cases have highlighted the fact that human errors can occur. These errors may be attributed to a variety of human factors that may affect the examiner, such as health problems, stress, inadequate training, or insufficient resources. In December 2008, we partnered with the National Institute of Justice to sponsor the Expert Working Group on Human Factors in Latent Print Analysis. This Working Group assessed the effects of human factors on forensic latent print analysis and recommended ways to reduce the likelihood and consequences of human error at various stages in the interpretation of latent print evidence. In February 2012, we published Latent Print Examination and Human Factors: Improving the Practice through a Systems Approach, which documents the Working Group’s findings and recommendations, addressing issues such as the acquisition of impressions of friction ridge skin, courtroom testimony, laboratory design and equipment, and research into emerging methods for associating latent prints with exemplars. It provides a comprehensive discussion of how human factors relate to all aspects of latent print examinations.
Contact: Melissa Taylor, 301-975-6363

Human Factors Issues Tracking Tool
In order to get a better understanding of the human factors that can affect latent print examination, we have created an online tool for latent print managers and supervisors to document errors and to determine the factors that lead to the error, the Online Human Factors in Latent Print Examination Portal. This study, which uses the human factors and analysis classification system (HFACS) model, will contribute to developing system-based approaches for minimizing error in forensic settings.
Contact: Melissa Taylor, 301-975-6363

Latent Print Examiner Personnel Selection Tool
Forensic laboratory managers need to know whether the people they want to hire have the right aptitudes, experience, and skills to be able to handle their work assignments. To help in the selection of latent print examiners, we have supported the development of a simple test that quantifies the cognitive processes that underpin fingerprint examinations. These tests use partial features of abstract designs to determine an individual's ability to match the partial image to the correct larger image with varying levels of quality. To account for time needed to produce a response and the closeness of incorrect responses, the tests are scored on a sliding scale. This test is now available to forensic practitioners through Cognitive Profile Testing.  Examples of testing images are available on the Latent Print Examiner Personnel Selection Test Examples page.
Contact: Melissa Taylor, 301-975-6363

Latent Print AFIS Interoperability Working Group
Automated fingerprint identification systems (AFIS) allow latent print examiners to search fingerprint files and to transmit fingerprint images. However, examiners often lack the technological ability to access AFIS in neighboring jurisdictions. In addition, before submitting a print for an AFIS search, examiners must manually encode the print’s features in a way that the system can understand. To address these issues, we partnered with the National Institute of Justice to convene the Latent Print AFIS Interoperability Working Group in April 2008. This Working Group is developing many documents to assist forensic scientists and managers, such as writing guidelines for memoranda of understanding between agencies, writing guidelines for new AFIS requests for proposals, and a glossary of AFIS terms. These documents are currently published in draft form.
Contact: Melissa Taylor, 301-975-6363

National Ballistics Imaging Comparison

We have partnered with the Bureau of Alcohol, Tobacco, Firearms, and Explosives to develop standards for ballistics identification in crime laboratories within the National Integrated Ballistics Information Network, which allows examiners to search digital images of markings on fired cartridge cases against a national database of images. This project establishes traceability and quality assurance in crime laboratories throughout the country. From 2008 to 2009, examiners helped us develop a Traceability and Quality System with our standard bullets and casings as references. The next phase of this project is currently underway.
Contact: Robert M. Thompson: 301-975-2118

2D and 3D Topography of Bullets and Casings
Marks on cartridge cases that have been fired from a firearm are often manually compared by a trained forensic examiner. Although the results of this comparison are generally accepted in courts, it is ultimately a subjective process. To help make the process more objective, we have been working with the Physical Measurement Laboratory to produce a mathematically based acquisition and comparison method. This method will further demonstrate the foundation of the science of firearm and toolmark identification and the usefulness of surface topography measurement techniques for this purpose.
Contact: Robert M. Thompson: 301-975-2118

Standard Bullets and Casings
We have also contributed to the development of the NIST standard bullets and casings. These serve as reference standards for crime laboratories to help verify that their computerized optical-imaging equipment is operating properly.
Contact: Robert M. Thompson: 301-975-2118

Digital Fingerprint

Additional Resources

We are contributing to the development of Standard Reference Materials (SRM) related to standard casings. We have created a set of master casings and are working on the decay factor and additional evaluations. The final SRM, which will be available on the SRM page, will provide virtual signature standards for casings to be used with equipment that captures images for comparison purposes.

Completed SRMs in the area of pattern and impression evidence include:

There are several Scientific Working Groups that provide information related to pattern and impression evidence, such as: