Polygraph Glossary Scoring

PolyScore

Definition

A proprietary computerised scoring algorithm developed by Dr. Don Krapohl and colleagues at Johns Hopkins University Applied Physics Laboratory. Uses linear discriminant analysis and Bayesian probability to classify examinees as deceptive or truthful. Integrated into Lafayette and other polygraph instrument platforms. Demonstrated accuracy rates of 85–92% under laboratory conditions.

What Is PolyScore?

PolyScore is a polygraph scoring concept. A proprietary computerised scoring algorithm developed by Dr. Don Krapohl and colleagues at Johns Hopkins University Applied Physics Laboratory. Uses linear discriminant analysis and Bayesian probability to classify examinees as deceptive or truthful. Integrated into Lafayette and other polygraph instrument platforms. Demonstrated accuracy rates of 85–92% under laboratory conditions.

Role of PolyScore in Polygraph Scoring

Scoring methodology is one of the most critical factors affecting polygraph accuracy. The evolution from subjective global evaluation to structured numerical scoring and automated algorithms has significantly improved the reliability and reproducibility of polygraph results, as measured by interrater reliability studies.

Modern scoring approaches analyse physiological responses across multiple channels — electrodermal activity (considered the most diagnostically powerful single channel), respiratory patterns, and cardiovascular changes — using validated Kircher features that have demonstrated replicable diagnostic value across decades of research.

Practical Application

APA Standards of Practice require the use of validated scoring methods for all diagnostic and screening polygraph examinations. The choice of scoring system directly affects the cut-scores applied for classification decisions (Deception Indicated, No Deception Indicated, or Inconclusive) and the overall balance between false positives and false negatives.

Related Terms

Understanding PolyScore in context requires familiarity with several related polygraph concepts:

Key Takeaways

PolyScore is an important concept within the field of Psychophysiological Detection of Deception. Whether you are a polygraph examiner, student at an APA-accredited training program, legal professional evaluating polygraph evidence, or a private individual preparing for a lie detector test, understanding this term and its relationship to other polygraph concepts will help you navigate the field with greater confidence and knowledge.

The science of polygraph testing has evolved significantly over more than 100 years, from the early work of William Moulton Marston and Leonarde Keeler to today's digital instruments and validated scoring algorithms. Every term in this glossary represents a piece of that scientific and professional heritage. For a comprehensive overview, visit the Polygraph Examiner Hub or use our examiner selection guide to find a professional examiner near you.

Cross-references

More scoring terms in this glossary

7-position scale The 7-position scale is the most widely used system for assigning numerical values to physiological responses in PDD ... Either-Or Rule The Either-Or Rule is a scoring rule developed by Cleve Backster used exclusively in the Backster Zone Comparison Tec... likelihood ratio The likelihood ratio (LR) indicates how much a polygraph result changes the probability of deception compared to pre-... CPSComputerized Polygraph System A computerised scoring system developed by Scientific Assessment Technologies based on University of Utah research. A... event marker Event markers are annotations placed on the polygraph chart to alert reviewers of significant events: question onset ... Two-Stage Decision Rules A decision framework in the Empirical Scoring System (ESS) that uses two sequential rules: Stage 1 applies the Grand ...

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