Addressing the National Academy of Sciences’ Challenge: A Method for Statistical Pattern Comparison of Striated Tool Marks

Authors

  • Nicholas D. K. Petraco Ph.D.,

    1. Department of Sciences, John Jay College of Criminal Justice, City University of New York, 899 10th Avenue, New York, NY 10019.
    2. Faculty of Chemistry, Graduate Center, City University of New York, 365 5th Avenue, New York, NY 10016.
    Search for more papers by this author
  • Peter Shenkin Ph.D.,

    1. Department of Mathematics and Computer Science, John Jay College of Criminal Justice, City University of New York, 899 10th Avenue, New York, NY 10019.
    Search for more papers by this author
  • Jacqueline Speir M.S.,

    1. Department of Chemical and Physical Sciences, Forensic Science Program, Cedar Crest College, 100 College Drive, Allentown, PA 18104.
    Search for more papers by this author
  • Peter Diaczuk B.S.,

    1. Department of Sciences, John Jay College of Criminal Justice, City University of New York, 899 10th Avenue, New York, NY 10019.
    2. PEDICO Research, RR2 Box 62, Waymart, PA 18472.
    Search for more papers by this author
  • Peter A. Pizzola Ph.D.,

    1. Special Investigations Unit, 421 East 26th Street, New York, NY 10016.
    Search for more papers by this author
  • Carol Gambino M.S.,

    1. Department of Sciences, Borough of Manhattan Community College, City University of New York, 199 Chambers Street, New York, NY 10007.
    Search for more papers by this author
  • Nicholas Petraco M.S.

    1. Department of Sciences, John Jay College of Criminal Justice, City University of New York, 899 10th Avenue, New York, NY 10019.
    2. Petraco Forensic Consulting, 73 Ireland Place, Amityville, NY 11701.
    3. New York City Police Department Crime Laboratory, 150-14 Jamaica Avenue, Jamaica, NY 11432.
    Search for more papers by this author

Additional information and reprint requests:
Nicholas D. K. Petraco, Ph.D.
Department of Sciences
John Jay College of Criminal Justice
899 10th Avenue
New York, NY 10019
E-mail: npetraco@jjay.cuny.edu

Abstract

Abstract:  In February 2009, the National Academy of Sciences published a report entitled “Strengthening Forensic Science in the United States: A Path Forward.” The report notes research studies must be performed to “…understand the reliability and repeatability…” of comparison methods commonly used in forensic science. Numerical classification methods have the ability to assign objective quantitative measures to these words. In this study, reproducible sets of ideal striation patterns were made with nine slotted screwdrivers, encoded into high-dimensional feature vectors, and subjected to multiple statistical pattern recognition methods. The specific methods employed were chosen because of their long peer-reviewed track records, widespread successful use for both industry and academic applications, rely on few assumptions on the data’s underlying distribution, can be accompanied by standard confidence levels, and are falsifiable. For PLS-DA, correct classification rates of 97% or higher were achieved by retaining only eight dimensions (8D) of data. PCA-SVM required even fewer dimensions, 4D, for the same level of performance. Finally, for the first time in forensic science, it is shown how to use conformal prediction theory to compute identifications of striation patterns at a given level of confidence.

Ancillary