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Forensic Linguistics: Recognizing Individual Written and Spoken Word Usages and Characteristics
Angela Lack, Law and Science Fellow
Introduction
Forensic linguists provides two functions: determining what text means and who wrote it.1 Experts in this field assist with investigations and have worked with attorneys in this capacity for over 20 years.2 The 1993 Daubert decision, which holds that trial judges must conduct a two-pronged test of admissibility by evaluating proffered expert witnesses to determine whether their testimony is both “relevant” and “reliable”, increased the need for testimony from forensic linguistic experts and made it imperative to prove scientific reliability of forensic linguistic findings.3 These experts are now being called to the witness stand to analyze spoken words and handwritten or computer-generated documents.
Forensic Linguistics
Forensic linguists focus on “the theoretical position that every native speaker has their own distinct and individual version of the language they speak and write, their own idiolect, and the assumption that this idiolect will manifest itself through distinctive and idiosyncratic choices in texts.”4 To determine individualized meanings or authenticity, linguists study syntax, or the way in which words are combined to make phrases.5 These syntactical structures are measured by complexity, categorized by the terms of the complexity, and then run through statistical procedures.6 Linguists also study patterns of speech sounds, how words are combined, how sentences are formed, the meaning or conveyed meaning of words, and the changing nature and variability of language.7 In addition to these tools, linguists sometimes rely on common sense and awareness to determine if someone else is imitating the writing of another.8
Forensic linguistic experts are skilled in numerous areas to help solve crimes or to help prove the guilt or innocence of the accused. These areas include (1) voice identification, such as determining whether the voice on a threatening tape was the defendant; (2) author identification, which compares the document in question to that of a known writing sample; (3) discourse analysis, which analyzes the structure of written or spoken words, to determine what topics are discussed and if the defendant agreed to partake in criminal endeavors; (4) linguistic proficiency, to determine if a suspect understood the Miranda warning or police caution; and (5) dialectology, focusing on the dialect of the defendant and comparing it to the dialect of the speaker on the incriminating tape recording.10 Dialectology differs from voice identification because voice identification analyzes the acoustic qualities of the voice.
To comply with Daubert, statistical information has become more complex, producing mathematical proof of the accuracy of the expert’s identification of the document’s author.11 However, some courts have limited the testimony of forensic linguistic experts to the comparison of the ‘markers’ between the compared writings; sometimes courts exclude the testimony of the expert with regard to extrinsic factors and their opinion of the authorship of the ‘questioned’ writing.12 When allowed to testify, most forensic linguistic experts testify for the defense because there is less burden of proof.13 In most cases, the expert can say with confidence that the person on the tape is not the voice of a certain person or that it is not likely that a certain person was the author of a particular written piece.14 Therefore, it is easier to eliminate a person than to prove beyond a reasonable doubt that the person is the speaker or author.15
The Written Word
While each person has a unique style of handwriting, forensic linguistics focuses on the way in which a person uses a word or phrase rather than the unique characteristics of their handwriting. Determining whether a writing is an imitation can be as simple as knowing that a elementary school dropout will not use sophisticated words in a confession or as complicated as determining that a certain word or phrases is specific to a dialect.16 One issue with author identification of documents is the length of the document. In most cases, the document (such as a ransom note or threatening letter) is too short to make reliable identifications.17 Forensic linguistic experts typically compare the writings of a known person to those of an unknown author. For example, Brian David Hummert was convicted of killing his wife after he claimed that a stalker sent notes to his wife.18 In addition to the notes from the stalker, the police received letters from a “serial killer” claiming to have killed Hummert’s wife.19 Professor Robert Leonard from Hofstra University compared the letters to Hummert’s writing and discovered that the stalker, serial killer, and Hummert had a pattern of never using contracting positive verbs, such as using “I am” instead of “I’m”.20
In one case, the murder suspect sent text messages from the victim’s cellular telephone to her friends and her father days after the murder to make them believe she was still alive.21 The police gave Professor Malcolm Coulthard the three July text messages sent to the victim’s friends and father, 100 samples of the July text messages, and 11 samples of text messages sent by the victim.22 Text messaging is rather short and most people make up their own style of sending text messages; therefore, making them more distinctive than other writings.23 While the texts sent by the victim and the July texts looked similar, upon closer review, Coulthard noticed differences.24 For example, both the victim and the 3 July texts used “2” instead of “to”; however, the victim did not leave a space between the “2” and the next word, while the 3 texts sent in July had a space before the next word.25 Other differences were more apparent, such as the victim’s use of “Im” and “Im not” rather than “I am” and “aint.”26 Other words used by the victim, such as “my”, “cu”, and “fone”, appeared as “me”, “cya”, and “phone” in the July texts, leading Coulthard to determine it was highly unlikely the victim sent the text messages.27
Another example of written analysis is focusing on misspelled words. In order to help determine the guilt of the murder suspect, Coulthard analyzed text messages, two suicide notes, and writing samples the suspect gave to the detectives.28 Similarities between the 3 July texts and the writing samples of the suspect were indicated through the misspelling of the word “off”, spelled “of” and the word “might”, spelled “mite”.29 An expert can determine when a highly educated person attempts to portray that he was poorly educated by misspelling simple words, such as cops (spelled “kops” in the letter), but correctly spelled complex words.30
Forensic linguistic experts use other methods of comparison such as transposition of verbs, which helped identify the Unabomber, or the similar and unusual spacing between words, which helped lead to the conviction of a surgeon who murdered his wife and then tried to blame someone else by writing an anonymous letter.31 Another mistake or error that linguists look for in documents is ‘competence errors’, which are differences from standard rules that the writer uses consistently.32 The linguist focuses on the grammatical or orthographic rule-breaking in short documents and only examines characteristic vocabulary in longer documents because more textual context is needed to determine vocabulary preferences.33
Forensic linguistic experts also provide testimony in non-criminal cases. A forensic linguist can testify in trademark disputes to help determine if the similarity or difference between two trademarks would be significant enough to confuse people.34 The forensic linguist focuses on how the words sound, the smallest component of the language.35 In addition to how a word sounds, a forensic linguist would also look at the meaning of the word to determine similarity.36
The Spoken Word
Analysis of the spoken word generally relates to tape recorded conversations or messages, such as undercover police recordings, voicemail messages, or answering machine messages.37 Each speaker builds his/her own active vocabulary, which differs from others, in terms of actual words or in preference of word choices.38 Forensic linguistic experts, such as Dr. Robert Shuy, specialize in ‘discourse analysis,’ which determines what a person is thinking based upon subjects raised in the conversation.39 Once the topics of the conversation are determined, the expert then looks at which person initiated the conversation in regard to the topic, who responded, and how the person responded and then subjects the information to linguistic analysis.40 For example, analysis of covert recordings may show the suspect's use of "I" rather than "we" indicating noncomplicity in a conspiracy, or the suspect’s use of the word "yeah" or "uh-huh", may not show that the suspect necessarily agrees, but may simply provide a feedback marker indicating he has understood the utterance.41 However, conflicting court decisions exist as to whether discourse analysts can testify as experts; however, even when they are not allowed to testify, attorneys may use them to help prepare the case.42 While this method will not give an exact indication of what the speaker’s intentions truly are, it does provide useful hints to what is on their mind and what is not on their mind.43
Another method of analyzing speech includes breaking down the speech into its smallest unit and counting syllables to make clear a disputed transcript.44 For example, by counting syllables in the sentence “I’ll take the bribe, wouldn’t you?” or I wouldn’t take a bribe, would you?”45, the linguist could determine what the suspect in a bribery case said on a recording.46
Computer analysis
Advances in technology and science now allow experts to compare documents and voice recordings quicker and more easily. Computer use, such as the Federal Bureau of Investigation's Communication Threat Assessment Database (CTAD), makes it possible to break communication into 23 different categories.47 These developments promise continued expansion of forensic linguistics.
Conclusions
Forensic linguistic experts use the written and spoken word to determine many characteristics and patterns in anonymous writings and covert recordings. These traits, utterances, unique abbreviations, and grammatical style or formatting are used to help link to a known individual, thereby leading to greater certainty in evidentiary analysis.
Up
1Malcolm Coulthard, “Some Forensic Applications of Descriptive Languages,” 2005 (Available at www.business-english.ch/downloads/Malcolm%20Coulthard/Forensic.applications.pdf ) (Last accessed on June 20, 2008).
2Dick Dahl, “Forensic Linguists Make a Science of Syntax,” LawyersUSA, April 7, 2008, (Available at http://www.lawyersweeklyusa.com/index.cfm/archive/view/id/430469) (Last accessed on June 20, 2008).
3Id.
4Malcolm Coulthard, “…and then… Language Description and Author Attribution,” 2006 (Available at http://www.aston.ac.uk/downloads/lss/english/Andthen_Coulthard.pdf) (Last accessed on June 20, 2008).
5Dahl, supra.
6Id.
7Ann Geracimos, “CSI: Language Analysis Unit; Forensic Linguists Solve Crime Using English Mastery,” The Washington Times, p. B01, January 16, 2006.
8Id.
9Peter Tiersma, “What is Forensic Linguistics?,” (Available at http://www.languageandlaw.org/FORENSIC.HTM) (Last accessed on June 19, 2008).
10Id.
11Dahl, supra.
12United States v. Van Wyk, 83 F. Supp. 2d 515 (D. New Jersey 2000).
13Tiersma, supra.
14Id.
15Id.
16Geracimos, supra.
17Tiersma, supra.
18Dahl, supra.
19Id.
20Id.
21Owen Amos, “The Text Trap,” The Northern Echo, February 27, 2008 (Available online at http://www.thenorthernecho.co.uk/features/leader/display.var.2076811.0.the_text_trap.php) (Last accessed on June 20, 2008).
22Id.
23Id.
24Id.
25Id.
26Id.
27Id.
28Id.
29Id.
30Dahl, supra.
31Geracimos, supra.
32Coulthard, supra n. 1.
33Id.
34Dahl, supra.
35Id.
36Id.
37Id.
38Coulthard, supra n. 1.
39Dahl, supra.
40Id.
41Tiersma, supra.
42Id.
43Dahl, supra.
44Geracimos, supra.
45Id.
46Id.
47 Geracimos, supra.
