NAS 1979 Report
Definition
The National Academy of Sciences report 'On the Theory and Practice of Voice Identification,' which concluded that spectrographic voice identification lacked the scientific foundation to support forensic individualisation claims, including standardised criteria, independent proficiency testing, and validated error rates.
- Publisher
- US National Academy of Sciences
- Title
- On the Theory and Practice of Voice Identification
- Subject
- Spectrographic voice identification
- Conclusion
- Lacked scientific foundation for forensic individualisation claims
Common questions
What specific gaps did the 1979 report identify in spectrographic voice identification practice?+
It found the method lacked standardised examination criteria, had not undergone independent proficiency testing of examiners, and had no established, validated error rates, meaning practitioners' individualisation claims were not supported by the kind of scientific validation courts expect for identification evidence.
Did the 1979 report end the use of voiceprint evidence in courts?+
It significantly damaged the method's scientific credibility and led many courts to restrict or exclude spectrographic voiceprint identification testimony, though acceptance had already been inconsistent across jurisdictions before the report, and some limited uses persisted afterward under stricter scrutiny.
How does this report connect to modern forensic voice comparison methods?+
Modern approaches, such as auditory-acoustic and likelihood-ratio-based forensic speaker comparison, developed partly in response to the deficiencies the 1979 report identified, aiming to build in the validation, error-rate reporting, and standardisation that spectrographic voiceprint analysis lacked.
Related terms
- Daubert Standard
- The US federal evidentiary standard (Daubert v. Merrell Dow Pharmaceuticals, 1993) requiring that expert testimony be based on scientifically valid methods with...
- ENFSI BPM
- The ENFSI Best Practice Manual for Forensic Comparison of Speech (2015, rev. 2022); the operational standard for speaker comparison in European forensic...
- Formant
- A resonance peak in the vocal tract filter; F1 and F2 together characterise vowel quality (height and frontness), while F3 and higher...
- Frye Standard
- The US legal test for admissibility of scientific evidence, originating from Frye v. United States (1923), which required that a technique be...
- IAVI (International Association of Voice Identification)
- Organisation founded by Kersta in the late 1960s to train and certify forensic voice identification examiners in the spectrographic comparison method. Certification...
- Likelihood Ratio (LR)
- The ratio of two conditional probabilities: the probability of the observed evidence given the prosecution's hypothesis (same source), divided by the probability...
- Proficiency Testing
- An external quality assurance programme in which a laboratory analyses blind samples distributed by an independent provider and submits results for comparison...
- Sound Spectrograph
- An instrument that plots the frequency content of a speech signal over time, with frequency on the vertical axis, time on the...
- Voiceprint
- Lawrence Kersta's 1962 term for the claim that the spectrographic pattern of an individual's speech is unique enough to serve as a...