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© 2011 flO[Special Contribution]

The Linguist as Expert Witness

Malcolm Coulthard
Aston University

This article looks at some of the problems faced by linguists who choose to act as expert witnesses
and some of the solutions they have produced. The chapter begins with an illustration drawn from linguistic evidence presented in a famous American trademark case. It then moves on to discuss the laws
on expert evidence in different English speaking adversarial jurisdictions, concentrating in some detailon the American Daubert criteria and their significance for linguistic evidence. The chapter then examines and evaluates differing ways of expressing opinions, the semantic and the statistical and ends
with examples taken from the author's evidence in two cases which went to Appeal in the Royal
Courts of Justice in London.
Keywords:

Court, Evidence, Expert, Forensic Linguistics, Witness

Scenario
In 1997 McDonald's Corporation took Quality Inns International, Inc, to court
claiming that they had ownership not simply of the name McDonald's but also of theinitial morpheme 'Me' and therefore could prevent its use in other trademarks. Quality
Inns had announced they were going to create a chain of basic hotels and call them MeSleep, claiming, when challenged, that they hoped the 'Me' prefix would evoke a Scottish link and with it the Scots' well-known reputation for frugality. McDonald's, who
had previously successfully prevented the use of the name McBagel's when a judge had
decided that the 'Me' prefix could not be used in conjunction with a generic food product, decided to challenge the McSleep mark, claiming it was a deliberate attempt todraw on the goodwill and reputation of the McDonald's brand.
In developing their case McDonald's pointed out that they had deliberately set out,
in one advertising campaign, to create a 'McLanguage' with Ronald McDonald teaching
children how to 'Me-ise' the standard vocabulary of generic words to create 'McFries',
McFish', McShakes' and even McBest'.
Fanciful as this linguistic imperialism might seem to ordinary users of the language, particularly to those of Scottish or Irish descent who would seem to be in dangerof losing their right to use their own names as trademarks, the lawyers took the claim
very seriously. Quality Inns' lawyers asked linguist Roger Shuy to help with two lin38

The Linguist as Expert Witness

39

guistic arguments, firstly, that the morpheme 'Me' was in common use productively, incontexts where it was not seen to be linked in any way to McDonald's and secondly,that such examples showed that the prefix, originally a patronymic and equivalent inmeaning to the morpheme son in Johnson, had become generic and thus now had ameaning of its own, which was recognisably distinct from both of the other major
meanings of 'son of' and 'associated with the McDonald's corporation'.
Shuy chose a corpus linguistics approach and searched to find real text instances ofwhat one might call 'Mcmorphemes'. Among the 56 examples he found were generalterms like McArt, McCinema, McSurgery and McPrisons, as well as items already being used commercially such as the McThrift Motor Inn, a budget motel with a Scottish
motif and McTek a computer discount store which specialised in Apple Mac computer
products. On the basis of such examples, Shuy argued that the prefix had become, inthe language at large, an independent lexical item with its own meaning of 'basic, convenient, inexpensive and standardized' (p. 99). Rather than resort to corpus evidence
themselves, McDonald's hired market researchers to access the public's perception of
the prefix directly and to do so through interview and questionnaire. The experts reported that their tests confirmed that consumers did indeed associate the prefix with
McDonald's, as well as with reliability, speed, convenience and cheapness. Faced withthis conflicting evidence, the judge ruled in favour of McDonald's, thereby giving themmassive control over the use of the 'Me' morpheme.
Of course, the successful defence of a trademark may occasionally have unwanted
consequences. In March 2007 McDonalds went to war again, this time against the Oxford English Dictionary, after it described a McJob as 'an unstimulating, low-paid job
with few prospects, [especially] one created by the expansion of the service sector'.
The company's chief people officer (sic) for Northern Europe insisted unsuccessfully
that the OED should change the definition to make it 'reflect a job that is stimulating,rewarding and offers genuine opportunities for career progression and skills that last alifetime'. In fact this was one further skirmish in the constant battle to maintain themark, because it was maintaining that the word 'mcjob' can only have one meaning 'a
job at McDonalds', which is patently not what it is used and understood to mean by thegeneral population.

Introduction

In the past twenty years, there has been a rapid growth in the frequency withwhich Courts in a number of countries have called upon the expertise of linguists incases where there is a dispute about aspects of a written text - I will not treat here therelated, but methodologically very different, discipline of forensic phonetics to which abrief introduction can be found in Coulthard and Johnson (2007, Chapter 7) and a much
more detailed one in Rose (2002). The cases in which linguistic evidence has beenused range from disputes about the degree of similarity in pronunciation and therefore

40

confusability of trademarks (Gibbons (2003: 285-7) and the meaning of individual
words in jury instructions (Levy 1993), through the 'ownership' of particular words andphrases in a plagiarism case, (Turell 2004), to accusations of fabrication of whole texts
in certain murder cases (Coulthard 2002). Usually the linguist uses standard analytic
tools to reach an opinion, although few cases require exactly the same selection fromthe linguist's toolkit. Occasionally, though, cases raise new and exciting questions fordescriptive linguistics, which require basic research, such as how can one measure the'rarity' and therefore the evidential value of individual expressions (Coulthard 2004) or
the reliability of verbal memory (Coulthard and Johnson 2007: 132-5).

On becoming a linguistic expert
For linguists wanting to move into expert witness work the criteria vary fromcountry to country. Australia and Britain share essentially the same position,
which is that it is the expert rather than the method that is recognised and socourts can allow expert opinions from anyone considered to have specialised
knowledge based on ... training, study or experience [provided that the opinionis] wholly or substantially based on that knowledge. (Australian Evidence Act
1995 Sec 79)
Usually, once an expert has been accepted by one court, s/he will be accepted unchallenged by other courts at the same level. The expert is retained and paid by one
side, but even so, legally s/he is 'appointed by the court' (Bromby 2002: 21) and since2007 experts in Britain have had to include in their reports a statement to confirm thatthey have provided an objective, unbiased opinion.
There are, however, so far no explicit rules in Britain, as there are in the USA following the Daubert ruling (see below), on the nature of the theoretical position or the
methodology or the evidence on which the expert bases his/her opinion and so, once anexpert has been retained, the court will determine, 'ad hoc, the sufficiency of expertiseand the relevance of that expertise to each case in question' (Bromby 2002 9). As partof this process both the competence of the expert and the reliability of the method(s) s/
he has used can be subjected to detailed examination, which can last for many hours.
Even after deciding to allow an expert to give evidence, the judge(s) and/or the jury
may decide the evidence is not helpful, persuasive or relevant and ignore it and occasionally, at the end of a trial, experts are severely censured by the court and/or particular methodologies deemed to be unacceptable (Hardcastle 1997).

The United States
Unlike the Anglo-Australian system, the American legal system approves thetechnique(s) that a witness uses rather than the witness him/herself. Rule 702 of theThe Linguist as Expert Witness

41

Federal Rules of Evidence allows an expert to testify as a witness if:
the testimony is based upon sufficient facts or data, [and]the testimony is the product of reliable principles and methods, andthe witness has applied the principles and methods reliably to the facts of thecaseRule 702 is designed to take account of the 1993 Daubert Ruling (explained below)
which dramatically changed the nature of allowable evidence and distanced the American system even further from the Anglo-Australian one. In what follows, I draw substantially on Tiersma and Solan (2002) and Solan and Tiersma (2004), which readers
are advised to study in their entirety.
There have been three stages in defining the admissibility of expert evidence in the
United States. Until 1975, the main standard for evaluating expert testimony was the
Frye test, named after a ruling in a 1923 case involving the admissibility of lie detector
evidence, which required there to be general acceptability of the principles and/or methodology which the expert had used:while courts will go a long way in admitting expert testimony deduced from awell-recognized scientific principle or discovery, the thing from which the deduction is made must be sufficiently established to have gained general acceptance in the particular field in which it belongs, (293 F. at 1014, as quoted inTiersma and Solan (2002, 223.).
As time went by Frye came to be seen as too rigorous. It was argued that scientificknowledge advances by argument and dissent, so there was pressure to allow the judge
and/or jury to hear opinions from both sides when there was serious academic disagreement, and in 1975 the Federal Rules of Evidence were introduced with the following
observation on the admissibility of expert evidence:
if scientific, technical, or other specified knowledge will assist a trier of fact tounderstand the evidence or to determine a fact in issue, a witness qualified as anexpert by knowledge, skill, experience, training, or education, may testify thereto
in the form of an opinion or otherwise. (Rule 702 as quoted in Tiersma and Solan 2002, 223.)
Even so, and confusingly, some federal courts continued to apply Frye until 1993, when
the Supreme Court ruled in the case of Daubert v. Merrell Dow Pharmaceuticals. The
main argument in that appeal was over whether expert evidence could be rejected on
the grounds that the experts involved had not published their work and had thereby
failed to meet the Frye test. In their ruling the Supreme Court observed that 'the adjective "scientific" implies a grounding in the methods and procedures of science' and thenwent on to propose four criteria with which to evaluate 'scientific-ness':

1.
2.
3.
4.

whether the theory ... has been tested;
whether it has been subjected to peer review and publication;
the known rate of error; andwhether the theory is generally accepted in the scientific community.
(509 U.S. at 593 as quoted in Tiersma and Solan 2002, 224)

This ruling left open the question of whether it covered evidence which was descriptive
rather than theoretical, but a ruling in 1999, in the case of Kumho Tire Co. v. Carmichael, confirmed that it did:the general principles of Daubert apply not only to experts offering scientific evidence, but also to experts basing their testimony on experience. (119 S.Ct. 1173
as quoted in Tiersma and Solan 2002: 224)
So, where does that leave the American forensic linguist? On the positive side Tiersma
and Solan (2002: 221) note that:courts have allowed linguists to testify on issues such 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.
However, in other areas the situation is more problematic, partly, perhaps, because some
non-linguists have used some of the linguistic labels for methodologies which are notlinguistically sound. For example, the Van Wyk case in 2000 seemed to set a precedent
for excluding stylistic analysis, as the court refused to allow an expert to give evidence
about the authorship of disputed documents, but, as McMenamin (2002) points out, theexpert in the case had no qualifications in linguistics. McMenamin (2004) argues astrong case for the scientific nature of his own brand of forensic stylistics and therefore
for its acceptability under Daubert. Indeed, he shows, in a case study of the significant
documents in the Jon Benet Ramsey case (2004: 193-205), how to express opinions
statistically in terms of mathematically calculated probabilities. It appears that the linguistic area of discourse analysis may have suffered similar loss of credibility through a
non-linguist claiming expertise in the area. Tiersma and Solan quote a judge's observation in a 1984 case, State v. Conway, following evidence from a psychologist, that discourse analysis is a 'discipline allowing [the expert] to determine the intent of the
speaker in covertly recorded conversations', which shows just how much re-educationneeds to be done.
Nevertheless, it must be conceded that, in cases where conclusions depend on observations about the frequency or rarity of particular linguistic features in the texts under examination, many linguists would have considerable difficulty in stating a 'known
rate of error' for their results, even if this phrase is interpreted as a likelihood ratio. It
is for this reason that some linguists will be forced to change their way of reaching andThe Linguist as Expert Witness

43

presenting their opinions, while others may choose to see their role more as that of educator/teacher/'tour guide' than of opinion giver (Solan 1998).

Giving Opinions

The professional life of the expert linguist, as opposed to that of the academic linguist, can be very lonely, as the majority of experts work alone, on occasional cases andrarely go to court to give evidence: most of them average fewer than ten cases a year
and one court appearance every two years. For this reason, giving evidence in person
in court is, for the majority of forensic linguists, an uncommon and stressful event. As
Shuy observes
For those who have never experienced cross-examination, there is no way to emphasise how emotionally draining it can be .... Testifying is not for the weak atheart (2002: 3-4)
Nor indeed for the weak at stomach- one of my colleagues eventually gave up, aftersome 25 years as an expert witness, saying he could no longer cope with the vomiting
before every appearance in the witness box.
Once the data analysis has been done and an opinion reached, the linguist is facedwith two interactional problems: firstly, how can s/he best transmit the linguistic insights and findings in a written report to an audience of legal professionals, who also
consider themselves language experts and who, despite what was said above about theimpartiality of the expert, want to (mis-)use the findings to construct a complicated legal case for innocence or guilt; and secondly, if s/he is called to give oral evidence, thelinguist has to cope with the unusual interactional rules of the courtroom which involve
lawyers asking questions, notionally on behalf of the court, and the witness being expected to address his answers not to the questioning lawyer but directly to the judge
and/or jury. Even more difficult can be cross-examination which pits an expert, who
has sworn to obey the Gricean maxims of quality and quantity, "to tell the truth, thewhole truth and nothing but the truth", against a lawyer who is under no such constraints and can apparently at will imply what he may "believe to be false" and saythings for which he "lacks proper evidence", as well as cut off the expert in midftow sothat a partially completed truthful answer implies an untruth.
Maley (2000: 250), in an excellent paper examining linguistic aspects of expert
testimony, observes thatexpert witnesses, particularly if they are new and inexperienced, tend to be quite
unaware of the extent to which shaping and construction of evidence goes on ....
All too often they emerge frustrated from the courtroom, believing that they
have not been able to give their evidence in the way they would like and that
their evidence has been twisted and/or disbelieved.

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And this despite the fact that experts are generally allowed speaking turns that are on
average two to three times longer than those of other witnesses (Heffer 2002).
All expert witnesses face these communication problems, but the linguist has the
additional and unique problem that everyone in the court is in some senses an expert on
language. Indeed it is very difficult to call a linguist to give evidence on word meaning, because courts are mainly interested in two kinds of meaning: technical, that is legally defined meaning, for instance the meaning of 'dusk' in a statute which says 'The
park gates will be closed at dusk', and where 'dusk' will have been given a specificmeaning elsewhere in the statute of something like '30 minutes after sunset'; and commonsense meaning, which is what a jury, being a collective representative of the common man, thinks a word means - so much so that juries are normally denied access todictionaries within the jury room.
When acting as an expert the linguist will typically be asked first to write a report
expressing an opinion- (McMenamin 2002: 176-8 has a useful section on report writing) - and then later s/he may be asked to go to court to present and defend that opinion.
In 2002 Stuart Campbell was tried and convicted for the murder of his niece, Danielle. Part of the evidence against him was a couple of text messages sent to his phonefrom Danielle's phone shortly after she disappeared. The prosecution suspected that hehad actually sent them to himself using her phone and I was asked to compare the styleof the two suspect messages with a set of 70 which Danielle had sent over the previous
three days. Unfortunately there was no similar corpus of messages composed by Campbell to use for comparison purposes.
Below is the first of the suspect text messages:
HIYA STU WOT U UP 2.IM IN SO MUCH TRUBLE AT HOME AT MOMENT EVONE HATES ME EVEN U! WOT THE HELL AV I DONE NOW? YWONT U JUST TELL ME TEXT BCK PLEASE LUV DAN XXX
It displays a series of linguistic choices which were either absent from, or rare in, theDanielle corpus; for example, the use of capitals rather than sentence case, the spellingof 'what' as 'wot', the spelling in full of the morpheme 'one' in 'EVONE', rather thanits substitution by the numeral '1', the omission of the definite article in the abbreviation of the prepositional phrase 'AT MOMENT' and the use of the full form of theword 'text' rather than an abbreviation 'TXT' in the phrase TEXT BCK. The problem
was how to reach and then express an opinion on the likelihood that Danielle did or did
not produce the message.

Expressing opinions semantically
The majority of forensic linguists (and phoneticians) have traditionally felt thatthey were unable to express their findings statistically in terms of mathematical proba-

The Linguist as Expert Witness

45

bility and so expressed them as a semantically encoded opinion. Indeed, some experts
simply express their opinion without giving any indication to the court of how to evaluate its strength, or of how that opinion fits with the two legally significant categories of'on the balance of probabilities' and 'beyond reasonable doubt': However, a growing
number of experts now use a fixed semantic scale and attach that scale as an Appendix
to their report to enable the reader to assess the expert's confidence in the opinion s/he
has reached.
At the time of the Danielle case I was using the scale of opinions below, which I
had adapted from the 11-point scale devised by members of the International Association of Forensic Phoneticians:
Most Positive5'I personally feel quite satisfied that X is the author'
4'It is in my view very likely that X is the author'
3'It is in my view likely that X is the author'
2'It is in my view fairly likely that X is the author'
1'It is in my view rather more likely than not that X is the author'0'It is in my view possible that X is the author'-1'It is in my view rather more likely than not that X is not the author'-2'It is in my view fairly likely that X is not the author'-3'It is in my view likely that X is not the author'-4''It is in my view very likely that X is not the author'-5'I personally feel quite satisfied that X is the not author'
Most Negative

The opinion I gave was -2 on the above scale, i.e. that it was fairly likely that Danielle
had not written the text message, but I agonised long and hard over which semantic label would best convey my assessment of the strength of the evidence as indeed I had
with several previous cases. Broeders (1999) suggested that what was happening insuch cases was that:experts, in using degrees of probability, are actually making categorical judgements, i.e. are really saying yes or no. Even if they use a term like probably(not), I think they are subjectively convinced that the suspect did or did not produce the sample material. (Broeders 1999: 237)
That was certainly true for me. Broeders went on to observe that the choice of a given
degree of likelihood on a scale like this is irremediably subjective, which is why two
experts might reach opinions of differing strengths based on exactly the same data.
Even so, he stressed that a subjective judgement should not be condemned simply because it is subjective:
The crucial question is not whether [it] is subjective or objective, but whether it

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can be relied on to be correct (ibid.: 238).
Nevertheless, a growing body of opinion is opposed to the use of such semantic scales,
especially because, even when they are accepted by a court, an unsolvable problem remains - how can one be sure that judges and juries will attach the same meanings to
the labels as did the experts who chose and applied them? This point was broughthome to me in a court martial where I expressed my opinion as 'very likely' on theabove 11-point scale and another expert expressed her opinion as 'very strong support'
on a 9 point scale. Neither of us was allowed to say how many points there were on
our respective scales, let alone show the full scale nor even gloss the particular categorychosen, even though at the same time the defence lawyer did his best to persuade theother expert to lower her opinion from 'very strong' on the grounds that another expert
had evaluated exactly the same evidence as only 'strong'.
An added complication is that, at the end of the trial, the triers of fact themselves,the jury, are not allowed the luxury of degrees of confidence; they have to work with abinary choice of Guilty or Not Guilty. So, however hedged the individual expert's opinion is when s/he presents it, the judge and jury have ultimately to make a categoricaljudgement as to whether to interpret the evidence as supportive of the prosecution or
the defence case or as simply inconclusive.

Expressing opinions statisticallyBroeders (op. cit.) argued that one should be worried about opinions expressed semantically, not because they are subjective, but rather because far too often the experts
who use them are expressing their opinions in the wrong way. He, and later Rose(2002), noted that an expert can offer an opinion on two things:
firstly, on the probability of a hypothesis - so in linguistic cases, for example,
on the hypothesis that the accused is the speaker/writer - given the strength ofthe evidence which the expert has analysed; andsecondly, on the probability that the evidence would occur in the form and quantity in which it does occur, given the two hypotheses that the accused is and,crucially, also is not the speaker/writer.
Both authors recommend the second approach. Indeed Rose quotes Aitken (1995: 4) inarguing that the former type of opinion, which, he says, is tantamount to deciding on
the likelihood of the accused being guilty, is the exclusive role of the judges of fact andfor this reason responsible scientists must confine themselves to talking about the likelihood of the evidence. Rose supports his argument by pointing out that no expert canmake an estimate of the likelihood of guilt or innocence on the basis of the linguistic
evidence alone; only those with access to all the available evidence can assess the valueof each piece. So, for example, a forensic handwriting colleague of mine concluded,

The Linguist as Expert Witness

47

after exhaustive comparisons, that it was very likely on the basis of the evidence he had
analysed, that a disputed signature on an Irish will, which had been written with a ballpoint pen, was genuine. But then, fortunately before committing his opinion to paper,
he discovered that the will was dated before the invention of ballpoint technology!
Broeders and Rose both argue that not only does their approach have logic on its
side, but it also has the added advantage that it enables probability to be expressed statistically rather than semantically. Essentially the method involves first looking at thelikelihood of the prosecution hypothesis given the raw data on each of the particularfeatures being examined. For example, imagine an anonymous letter which includes thenon-standard spelling 'of course'. In attempting to support the prosecution hypothesisthat the accused wrote the letter we discover that 80% of a sample of attested letters
written by the suspect also display this feature. However, in support of the defence hypothesis that the accused was not the author, we discover that in the general population
writers also use the feature 10% of the time. How do we now assess the evidential
strength of this finding, i.e. that we would expect the suspect to use it 10% of the time
anyway, but that in fact slhe is using it much more?
To start with; we produce a likelihood ratio by dividing one percentage by the other, i.e. 80/10 and so get a likelihood ratio of 8. Interpretation of this ratio, however, is
not quite so simple. It is certainly true that, as Broeders (op. cit.: 230) expresses it, "tothe extent that the likelihood ratio exceeds 1 the evidence lends greater support to the[prosecution] hypothesis, [while] if it is smaller than 1 it supports the alternative hypothesis". Unfortunately, that doesn't tell us exactly how much greater support a likelihood ratio of 8 gives - we will return to this question of interpretation below.
A major advantage of this method of expressing the weight of evidence statisticallyin this way is that it allows the user to combine several pieces of evidence or rather
several likelihood ratios together, by multiplication, in order to produce a composite
likelihood ratio: when combined together, all ratios that are greater than 1 will increase
the overall likelihood, while any ratio of less than 1 will reduce it. So, to continue ourimaginary example, there might be a series of other distinctive features co-occurring in
the anonymous and attested letters like their spelled as there, you're spelled as your andpossessive its spelled as it's. These features may be found by themselves to have low
likelihood ratios of, respectively, 1.4, 1.5, 1.7, but when they are combined with thelikelihood ratio of 8 already calculated for ofcourse, they produce, by multiplication, themuch higher ratio of 28.56. In other words after examining the four features, we can
now say on a principled basis that it is 28 times more likely that the suspect wrote theletter than that a member of the sample general population did.
One strong argument in favour of this statistical approach is that it allows the easy
incorporation of counter indications as well. Whereas experts using the 'evidence toevaluate the hypothesis approach', as I was in the Campbell case, have to decide what
weight to give to any evidence which does not support the indication of the majority of
the features analysed - should they, for example, allow such evidence to reduce their

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opinion by one or two degrees of certainty or by none at all - by contrast, with a likelihood ratio approach, any measurement which supports the defence hypothesis, and so
by definition has a likelihood ratio of less than 1, will simply reduce the cumulative ratio. So let us now imagine we add in the feature whose spelled as who's, which has aratio for the letters under consideration of 0.85, the cumulative ratio will now fall to
24.28.
While such a statistical approach has obvious attractions, it does present very real
problems to both phoneticians and linguists when they try to calculate the defence likelihood ratio. Firstly, how does one establish what is a relevant comparison populationof speakers or texts, and how does one get access to, and then analyse, the data fromthat population, particularly in a world where lawyers and courts are not willing to pay
for what might be thought to be basic research. At least in the area of forensic phonetics there are already agreed reference tables for such things as pitch of voice and solid
evidence about the effects of telephone transmission on the pitch of the first formants ofvowels. In the area of linguistics there is even less reference data, although specialist
corpora are being created: McMenamin, for instance, (op. cit.: 154), reports using a corpus of 742 letters for comparison purposes and Grant and Olsson have created corporaof text messages. Of course for some purposes, (see Coulthard, 1993, 1994) evidence
can be drawn from already available general corpora like the Australian National Corpus, the British National Corpus, the Collins Bank of English and the American National Corpus.
But then, even if we are able to calculate the defence ratios, we are still not out of
the trees, because we need to know how to evaluate the significance of the resulting
composite likelihood ratios. And there is the added problem of whether a lay jury cancope with likelihood ratios, or whether they will simply introduce even more confusion.
Rose (op. cit.: 62) proposes solving this problem by grouping all numerical likelihood ratios, once they have been calculated, into five semantically labelled categories,
which, he suggests should be transparent to the jury:
Likelihood ratio
10,000+1,000-10,000
100-1,000
10-100
1-10

Semantic Gloss
Very strong
StrongModerately strong
Moderate
LimitedHowever, such a translation is by no means universally accepted.
Even if one accepts Rose's argument for the theoretical advantages of likelihood
ratios, there remain two major doubts. Firstly, after rejecting a scale of opinions expressed semantically, we have ended up with a scale of likelihoods expressed semantically, although admittedly this time, if two experts agree on the facts to be considered,they will necessarily agree on the likelihood ratio, too. Even so, the problem remains

The Linguist as Expert Witness49

of whether juries can and will interpret the semantic expression of the ratios as the expert intended. Secondly, we don't yet know how appropriate the labels are as glosses
for the ratios, even though the category cut-off points are numerically neat. On the one
hand, courts work with the concept of 'beyond reasonable doubt' which does not have adefined likelihood ratio, although a lay juror, along with statistician A. P. Dawid (200 1:4), might be happy to equate the phrase with one chance in a hundred. On the other
hand, one area of forensic investigation, DNA analysis, seems to be working with verymuch higher likelihood ratios:
His counsel, Rebecca Poulet QC, reminded him of DNA evidence which showed
his profile matched that of the attacker, with the chances of it being anyone else
being one in a billion. (http://news.bbc.co.uk/l/hilengland/3496207.stm)
In principle though, the judicial system should be attracted by the fact that likelihood ratios derived from a variety of types of evidence can be combined to produce acomposite likelihood ratio. In an ideal Rosean world, juries would have a statistician tohelp them weigh all the evidence, and, unlike the individual expert, the jury would be
able to take account as well of such prior odds as how many possible suspects there
are. For example, if there are five suspects, then before any evidence has been considered the odds that one of them is guilty are 114 = 0.25, if there are only two suspects
the odds are 1/1 = 1.
Despite obvious academic support for the use of likelihood ratios, it may be a longtime before they get general acceptance in courts. The Times (9 May 1996, p. 36) reported the opinion in an Appeal Court judgement (R v. Adams) where, in the original
trial, a statistician had been allowed to instruct the jury about both Bayes theorem andunderlying likelihood ratios and then how to create and sum the ratios in order to produce a composite ratio. The Appeal Court judges ordered a retrial and observed that,
although the likelihood ratio 'might be an appropriate and useful tool for statisticians ...
it was not appropriate for use in jury trials, nor as a means to assist the jury in theirtask'. After a second trial in which the same expert was allowed to instruct a different
jury, there was a second appeal, at the end of which the judges opined:
Introducing Bayes' Theorem, or any similar method, into a criminal trial plunges
the jury into inappropriate and unnecessary realms of complexity, deflecting
them from their proper tasks. Reliance on evidence of this kind is a recipe for
confusion, misunderstanding, and misjudgement.
(http://www.herkimershideaway.org/writings/bayes.htm)
And that, for the moment, is the situation in the British courts: experts are still able toexpress opinions without relating them to probabilities or likelihood ratios.

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Consulting and testifying as tour guides
So what remains for the linguist whose findings cannot be appropriately presented
in a statistical way? Solan (1998) addresses a problem which is unique to experts inlinguistics, the fact that the judges of fact, whether they be actual judges or jury members, are seen for most purposes to be their own experts in the area of language use andinterpretation - the law is, much of the time, concerned with the meaning(s) that ordinary speakers attach to words and expressions. Even so, there is a role for the linguist,
which is to explain and elucidate facts about language and usage as a result of whichjudge and jury will then be in the same position as the linguist and so can make linguistically informed decisions. In Solan's words:
my linguistic training has made me more sensitive to possible interpretations that
others might not notice and I can bring these to the attention of a judge or jury.
But once I point these out and illustrate them clearly, we should start on an
equal footing (p. 92).
To expand Solan's observation, linguists are not only 'experts in the nature of meaning'
but also experts in the nature of linguistic encoding at both lexico-grammatical and textual levels and so there is a guiding role for the linguist in these areas as well, both before and during a trial.
One British example of the expert sensitising the lay audience comes from my evidence in the Appeal of R v. Robert Brown. In Brown's disputed statement there occurs
the phrase my jeans and a blue Parka coat and a shirt. The accused claimed that amonologue confession attributed to him had in fact been elicited by question and answer and transformed by the interviewing officers into monologue form. As part of hisevidence in support of Brown's claim, I focussed on the two clauses "I was covered inblood," "my jeans and ~ blue Parka coat and ~ shirt were full of blood." To a linguist
it is clear that the phrasing of the subject of the second clause is most unnatural; no one
would refer to their own clothes with the indefinite article once they had begun a list
with the possessive determiner. The most likely use of 'a' in this context would be to
distinguish between 'mine' and 'not-mine'. For example, "I looked round the room andI saw my jeans and a blue Parka coat and a shirt, they were full of blood" would be
perfectly natural, but that meaning, of course, didn't make any sense in a narrative
where all the clothes referred to belonged to the narrator. The phrase "a blue Parka
coat and a shirt" could occur quite naturally, of course, as a result of a careless conversion of a sequence of short questions and answers into monologue form and one could
see how it might have happened by looking at the following sequence taken from therecord of an immediately preceding interview with Brown:
What were you wearing?
I had a blue shirt and a blue parka

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51

In this context the use of the indefinite article is normal; as just noted above, whenitems are introduced for the first time, the indefinite article is the natural choice. Oncethe oddity of the phrase and the occurrence of a similar phrase in the interview had
been pointed out the appeal court judges they were as competent as any linguist to draw
inferences from this oddity.
A substitute prosecution witness
One of the important points that Solan makes is that, although juries and judges
may well be able to process words, phrases and even sentences as well as any professional linguist, they may have problems with long documents or a series of related documents, because they may not be able to make the necessary links:
Of course a jury can read the document[ s]. . ... But not all jurors, without help,
can focus on a phrase in paragraph 24 of a contract that may have an impact on·
how another word should be interpreted in paragraph 55. (p. 94)
In the Paul Blackburn Appeal it was also important to draw the attention of the judges
to two phrases occurring in two different documents, one a record of a dictated statement, the other a record of an interview:i)StatementInterview

I asked her if I could carry her bags she said "Yes"I asked her if I could carry her bags and she said "yes"ii)StatementInterview

I picked something up like an ornament
I picked something up like an ornament

Linguists of most persuasions are in agreement that the likelihood of two speakers independently producing exactly the same phrasing reduces dramatically with the length ofthe expression and the likelihood of them choosing two or more identical phrasings iseven more unlikely. However, the linguist's 'knowledge' is the total opposite of lay belief. When faced with the problem of convincing the Appeal Court judges of the significance of the identical expressions, I chose the following procedure.
Firstly, I demonstrated that even short sequences of words can be unique encodings, by looking at the occurrences of the words 'I asked her if I could carry her bags'
in a series of Google searches. The results at the time were as follows:
Sequence
I askedI asked her
I asked her if
I asked her if I
I asked her if I could
I asked her if I could carry

No. of Occurrences
2,170,000
284,000
86,00010,400
7,770
7

52

I asked her if I could carry her
I asked her if I could carry her bags

40

Using these examples, I argued that, if there was not a single example of anyone having
ever produced this sequence, the chances of even longer sequences occurring twice indifferent documents was infinitesimal, unless, of course, one was derived from the other.
When, writing this chapter, I re-checked the Google figures for "I asked her if I could
carry her bags" and found, to my horror, not none but five instances of the phrase.
However, as the adage goes, it is the exception that proves the rule. There is now a
website devoted to Paul Blackburn's case which carries the disputed statement, so oneof the instances is the original saying, three of the others are web-versions of Coulthard(2004) which reports the case and the final instance is a Dutch university PowerPoint
quoting the example from Coulthard (2004). In other words the five instances are all
quotings of the same single saying.
To strengthen the argument used to the court, I accessed Google to find anothercase, this time one involving Lord Justice Rose, who was to preside at the trial. On
typing in the words 'Lord', 'Justice', 'Rose' and 'Appeal' the first three citations I
found were concerned with an appeal by a famous British politician - Lord Archer against his conviction for perjury. The first hit of all was:
Guardian Unlimited I Special reports I Archer loses appeal bid... was not present at today's hearing, had his application for permission to appeal against the conviction rejected within hours. Lord Justice Rose, sitting with... www.guardian.co.uk/archer/article/ 0,2763,759829,00.html
I accessed the full citation, which is reproduced in part below as Text 1, and from it selected the first phrase quoted from Lord Rose "For reasons we will give later in theday", which is highlighted in italics.
Text 1
Archer loses appeal bid
Lord Justice Rose, sitting with Mr Justice Colman and Mr Justice Stanley Burnton in London, told Archer's QC Nicholas Purnell: "For reasons we will givelater in the day we are against you in relation to conviction".
At the start of the hearing Nicholas Purnell QC, outlining the grounds of appeal,
said: "The submission that we make on behalf of Lord Archer is that the firstand fundamental ground which interconnects with all the other grounds of appeal was that the learned trial judge wrongly exercised his discretion not to sever
the trial of Edward Francis."
Mr Purnell said the decision of the judge, Mr Justice Potts, not to sever the trial
of Francis had an "unbalancing effect on the equilibrium" of the trial".
Counsel argued that Mr Francis was "in a position effectively as a substituteprosecution witness and a substitute prosecutor".

The Linguist as Expert Witness

53

Given the nature of Appeal Court judgements for reasons we will give later inthe day seems to be an unremarkable phrase for an appeal court judge to use,
particularly as a lot of judgements are produced some time after the verdict isannounced. Yet a search returned only seven occurrences. Every single one ofthem was about Lord Rose; indeed they were all reports of this same single utterance at the end of the Archer appeal.
I then took three other short phrases which I highlighted in italics in the extract above,
this time from Nicholas Purnell, Lord Archer's lawyer, each of them apparently not unusual phrases for a lawyer to utter, "the first and fundamental ground", an "unbalancing
effect on the equilibrium" of the trial and a "substitute prosecution witness". For thesephrases Google found 7, 10 and 4 instances respectively, but again all the instanceswere versions of the same single utterings.
This seemed to be a simple and efficient way of illustrating uniqueness of expression in court, but when I presented this illustration to the lawyers, they declined to submit it to the judges and one of them describing it as 'whimsical'.
However strong the expert feels the evidence to be, its successful presentation incourt, indeed whether it is even presented, depends crucially on the lawyers. Sometimes (the expert feels that) the lawyer omits essential facts during the Evidence in
Chief questioning, sometimes successful cross-examination neutralises some of thepoints and sometimes the evidence is used for other purposes in cross-examination.
And then there is the use to which no one has access, the jury deliberations. All experts would like to know how best to present their evidence for the benefit of the jury most would love to receive from the jury some equivalent of those end-of-module evaluation forms beloved of university administrators.

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