The Linguist on the Witness Stand: Forensic Linguistics in American Courts

It is becoming increasingly common for linguists to testify as expert witnesses in both civil and criminal trials. Often linguistic expertise is clearly helpful to the judge or jury. Based on published judicial opinions, from which we draw our data, it appears that courts have allowed linguists to testify on such issues as the probable origin of a speaker, the comprehensibility of a text, whether a particular defendant understood the Miranda warning, and the phonetic similarity of two competing trademarks. In other areas the admissibility of linguistic testimony has been more controversial, including author and speaker identification, discourse analysis, the meaning of legal texts, and the comprehensibility of jury instructions. Reasons for judicial reluctance to admit linguistic expertise include concerns that it is not sufficiently reliable, the belief that issues like the meaning of a text can just as well be decided by a jury, and sometimes even institutional and political considerations. Despite such reservations, courts generally recognize that there is a place for linguistic expertise in appropriate cases.*

Linguists are appearing with increasing frequency as expert witnesses in American courtrooms. Nonetheless, in many cases where one side or the other wishes to present linguistic evidence—either through testimony or some other means—the judge refuses to admit it. This raises questions of why courts are more receptive to linguistic expertise in some types of cases than in others, and when they ought to accept linguists as experts.

Linguistic issues can arise in a great variety of legal contexts. Specific subjects that linguists may address include the likelihood of confusion in trademark cases; miscommunication because of dialect differences; the comprehensibility of legal documents; the meanings of statutes, wills and contracts; the identification of authors and speakers; the ability of jurors to understand instructions, or of an arrested person to comprehend the Miranda warning; and many more. Almost any area of linguistics can be relevant in court. Phonetics, for example, is important in trademark cases where the sound similarity of two names is in question, as well as in speaker identification. Discourse analysis has been used to help jurors understand covertly recorded conversations in criminal cases. Syntax, semantics, and pragmatics are all relevant when the meaning of legal documents is at issue. Smaller subfields of linguistics may also have relevance in a legal dispute. Thus, a dialectologist might help identify the place of origin of a speaker on a tape-recorded bomb threat.

In this article, we will review some of the substantive legal areas in which linguistic expert testimony has been admitted, and others in which its admissibility has been more controversial. We will not focus on reports by forensic linguists themselves. Judith Levi (1994) has already published an overview of cases in which linguists have reported on their experiences in court, and Roger Shuy (1993, 1998) has written two books describing some of his experiences.¹ In contrast, we draw our examples from published judicial opinions in the United States. In almost all American jurisdictions, only published opinions can serve as precedents.² A court deciding whether to permit a linguist to testify is most likely to turn for advice to the record of published judicial opinions. We therefore think it is useful, for both the legal and linguistic communities, to investigate and report on that record.

Our legal research found over one hundred published judicial opinions, not counting voiceprint cases, in which language experts were mentioned. (We deal with the issue of voiceprints separately below.) Most of these are decisions by federal and state appellate courts. Often, the party who offered the testimony of an expert witness at trial appealed the trial court’s ruling not to allow such testimony. Because appellate review of evidentiary decisions under American law is very deferential to the trial court, such rulings are often upheld on appeal (Weinstein & Berger 1998). One might therefore get the impression that linguists only seldom participate in the judicial system, and are largely unwelcome. But this would be a serious misinterpretation of the facts for three reasons.

First, and perhaps most important, our analysis of the published...