William L. Fleisher

William L. Fleisher is a veteran law enforcement professional and polygraph examiner who served as Assistant Special Agent in Charge of the Philadelphia Office of the U.S. Customs Service, as a special agent with the Federal Bureau of Investigation, and as an officer with the Philadelphia Police Department. He has over 42 years of experience in law enforcement and investigation and has been a polygraph examiner since 1975. Fleisher is Director of Keystone Intelligence Network, Inc., and Assistant Director of the Academy for Scientific Investigative Training, where he has collaborated extensively with Nathan J. Gordon on polygraph techniques and training.

An internationally recognized expert in Behavioral Symptom Analysis, Fleisher is the author of the U.S. Customs technical manual on Behavioral Analysis. His contributions to polygraph research include studies on the Integrated Zone Comparison Technique (IZCT), which he investigated alongside Gordon to evaluate its effectiveness with various scoring systems. Research using the IZCT demonstrated 100% accuracy when inconclusive results were excluded, and 90% accuracy with the ASIT Poly Suite scoring system when inconclusives were counted as errors. Fleisher co-authored the influential textbook "Effective Interviewing and Interrogation Techniques" with Gordon, which covers forensic assessments based on psychophysiology and nonverbal behavior analysis.

Fleisher is a co-founder of the Vidocq Society, established in 1990 with forensic sculptor Frank Bender and psychologist Richard Walter. The Vidocq Society is a crime-solving club in Philadelphia named for 19th-century French criminologist Eugène François Vidocq, where law enforcement officials from around the world present cold cases for review by forensic professionals. Fleisher continues to serve the Society as its Commissioner Emeritus. He is also a member of the American Polygraph Association, International Association of Chiefs of Police, American Board of Forensic Examiners, and is a Certified Fraud Examiner.

Fleisher's work bridges multiple domains of investigative science. Beyond polygraph testing, he has lectured on polygraph and behavioral analysis for law enforcement and intelligence agencies in the United States and overseas. His expertise in behavioral symptom analysis—the systematic evaluation of verbal and nonverbal cues during interviews—has made him a sought-after consultant for both law enforcement investigations and private sector applications, including pre-employment screening and fraud investigations.