NCJ Number
66976
Journal
Arizona Law Review Volume: 21 Issue: 4 Dated: (1979) Pages: 1163-1186
Date Published
1976
Length
24 pages
Annotation
THIS ESSAY DISCUSSES THE TECHNIQUES OF VOICE SPECTROGRAPHY AND THE DEBATE AS TO ITS ACCURACY. IT REVIEWS LAW CONCERNING SPECTROGRAPHIC EVIDENCE AND THREE EVIDENTIARY STANDARDS USED BY COURTS.
Abstract
THE SPECTROGRAPH ANALYZES SPEECH SOUNDS, INDICATES HOW THEY VARY FROM INSTANT TO INSTANT, AND MAPS A SPECTRUM OF THE FREQUENCY AND INTENSITY OF EACH OVERTONE OF THE SPEECH WAVE, BUT DOES NOT ANALYZE VOICE PITCH. THREE FACTORS CAUSE VOICE CAVITIES AND PEAKS IN THE SPECTROGRAM: THE SPEAKER'S BODY DIMENSIONS THAT SET HIM APART FROM OTHERS, THE SPEAKER'S DIALECT, AND THE SPEAKER'S PARTICULAR METHODS OF MATCHING THE NORMS OF THE DIALECT. THE IMPROBABILITY THAT TWO SPEAKERS WOULD HAVE VOCAL CAVITIES OF THE SAME SIZE AND USE ARTICULATORS IDENTICALLY IS THE BASIS FOR THE CLAIM THAT EACH VOICE IS UNIQUE. ONE SCIENTIFIC REPORT CLAIMED THAT DIFFERENCES ON SPECTRUMS MIGHT INDICATE DIFFERENT SPEAKERS OR MERELY A VARIATION IN THE SPEECH OF A SINGLE SPEAKER, WHILE VOICE IDENTIFICATION EXPERIMENTS DEPEND STRONGLY ON EXPERIMENTAL CONDITIONS RATHER THAN ON DIFFERENCES IN VOICE CHARACTERISTICS. SPEECH PATTERNS ARE PHYSICAL CHARACTERISTICS AND SO THE VOICE IS OFTEN GROUPED WITH PHYSIQUE AND COLOR OF EYES AND HAIR, WHICH ARE HELD TO BE UNQUESTIONABLY OUTSIDE FIFTH AMENDMENT PROTECTION. SPEAKING INSIGNIFICANT SOUNDS FOR IDENTIFICATION PURPOSES IS NOT GIVING TESTIMONIAL EVIDENCE. ANOTHER LEGAL ISSUE CONCERNS THE RELIABILITY OF THE STANDARDS USED AND WHICH STANDARD IS BEST. THE FRYE EVIDENTIARY STAND IS USED BY MOST COURTS WHEREBY THE COURT GATHERS OPINIONS OF SCIENTISTS THROUGH TESTIMONY, CASE LAW, COMMENTS, AND SCIENTIFIC ARTICLES. THE WILLIAMS STANDARD ONLY USES A GROUP THAT HAS DIRECTLY PARTICIPATED IN VOICEPRINT EXPERIMENTS. THE MCCORMICK STANDARD, USED MORE RECENTLY, RECEIVES ANY CONCLUSIONS SUPPORTED BY A QUALIFIED WITNESS AND WEIGHS THE PROBATIVENESS, MATERIALITY, AND RELIABILITY OF SCIENTIFIC EVIDENCE AGAINST ITS TENDENCY TO MISLEAD OR PREJUDICE THE JURY. THE ESSAY CONCLUDES THAT THE MCCORMICK IS THE MOST APPROPRIATE BECAUSE IT ALLOWS RELEVANT EXPERT TESTIMONY WITHOUT UNDUE RESTRICTION AND INSTRUCTS THE JURY THAT IT MAY REJECT THE TECHNIQUE OR THE CONCLUSIONS IF THEY ARE FOUND UNRELIABLE. FOOTNOTES ARE INCLUDED. (JLF)