top of page
  • Writer's pictureThe Paladins

How to spot a liar

Honesty is one of the most important virtues. In the immortal words of German philosopher Immanuel Kant:

Honesty is better than any policy. From the crooked timber of humanity, there is nothing that is straight that can be formed.

Indeed honesty is both divine and efficient. Kant developed both an ethical theory and an argument for the existence of God based upon the paramount nature of the virtue of honesty. His ethical theory, very approximately, worked as follows. His so-called "Categorical Imperative" involved the injunction that you should only act upon a precept that could properly be applied as a universal rule - in other words, a precept adopted by all people. This is one of the most famous ideas in the history of philosophy, and it expresses the feature of moral thinking of the kind that humans engage in as exhibiting a quality of equality. All people are morally equal, or all their actions have equal moral relevance. Different people should not be judged by different standards. The Prime Minister of a country should be held to precisely the same standards as his or her citizens. A moral rule is one that it is appropriate for everyone to follow.

From this notion came the duty of honesty, because Kant pointed out that if you adopted any other rule about when to tell the truth than always, then we would be in a shambles because nobody would be able to rely upon the words that each other uses. For Kant, even so-called "white lies" are excluded because if as a moral precept you give people discretion to lie when they think it might be convenient or beneficial, then this is just the beginning of a slippery slope in which everyone uses their subjective judgment to decide when to lie or not and morality is not concerned with subjective assessments but with objective law. Moreover, thought Kant, because humans are capable of thinking about moral rules in this way there must be some unknowable correspondent rule-maker out there who always tells the truth and never lies; and for Kant this is what we call God.

Now all this is rather academic if particularly striking in its imagery. But it reflects an underlying common sense theme that appeals to all of us, even though we all lie from time to time and we feel bad about it when we do, namely that there is no point in having language that refers to states of events if we are going to use it to describe false states of events. The capacity to refer to states of events, and facts, using language is what distinguishes us from the animals. Animals can use their own sorts of language for other purposes - to express emotions or mental states such as fear, joy, pain and the like. However what they cannot use language for is referring to objects. Dolphins have no word for water and gorillas have no word for tree (as far as we know - and if they did, then surely we would have worked it out by now given our advancements in artificial intelligence computational methods to mimic human languages).

So even though we all do it, we all recognise lying to be a bad thing and dishonest people are castigated. Some societies tolerate lying more than others; societies that tolerate lying less tend to look down upon societies that tolerate it more.

This leads to the question of how to tell whether someone is lying. The most obvious course is to cross-check what they say with other evidence or facts, and ultimately all lie detection of any value turns upon a variant of this. However humans have also come to associate certain behavioural reactions with lying. These include:

  • Nervousness

  • Evasiveness or hostility when pressed on details

  • Sweating

  • Not using grammatically complete sentences (although the youth of today are increasingly of that habit anyway)

  • Shifting eyes

  • Looking away

There are many such qualities associated with lying, and it is an art not a science to judge whether another person is telling the truth. Sometimes looking away does not mean a person is lying at all; it may mean they are concentrating or thinking carefully to try to get the details right. There is nothing more infuriating when a person is trying to recollect accurately what happened, particularly in events that took place some time ago, than to be accused of lying just because you take a while to answer the question.

This is also why you should never agree to a so-called "lie detector" test. Lie detectors measure things like sweating, movement of the pupils, increased heart rates, and similar such qualities, that some people associate with lying while in other people they have nothing to do with lying at all but may just be indices of heightened nervousness for example. This author has known at least one person who would fail every lie detector test ever devised; but he is scrupulously honest. He just spends his time extremely nervous whenever he is in any formal situation. Lie detectors are spurious technology and you should never agree to be examined by a lie detector, notwithstanding what you may watch in the movies.

The professionals in assessing when people are lying are of course lawyers, because they spend their lives dealing with people who are lying to them all the time. These people are variously called clients, defendants, and witnesses. They get so used to dealing with liars that they develop a series of instinctive and quasi-scientific skills to assess when a person is lying. The quasi-scientific skills are the ones of interest to us, because it is very difficult to teach a person how to have good instincts. They can only acquire good instincts through practice. Nevertheless before we turn to the quasi-scientific skill of lie detection, which we call cross-examination, we will share a couple of our instincts.

Firstly, it is lawyers' experiences that people's memory of routine events fades very rapidly, even if their memory of extreme events may persist. Moreover important details in extreme events (for example, the details of an aggressor's face and physique in a street attack) may quickly fade. That is why it is important to take an immediate written note of what happened in any event where the details might be relevant later. Lawyers write memoranda describing all manner of incidents that may potentially be relevant later, as soon as they can after the incident took place (whether it be a telephone call, a meeting, or some other event), not just because they are obsessed with taking notes of everything (which is an occupational hazard of being a lawyer) but also because lawyers know just how quickly memories fade. It is often difficult to remember the contents of a simple telephone call even an hour after the call took place. So you take an immediate written note if you can, and then formalise it into an electronic note as soon as the opportunity to do so arises. This is something that modern technology has facilitated, albeit with the consequence that modern trials have become much longer because they are awash with pieces of paper in which people have been making contemporaneous records of what was going on and then everyone has to read them.

Police officers also know the importance of taking contemporaneous notes. That is why they carry notebooks with them everywhere, with scrupulous rules about drawing lines under the ends of notes of specific events, having times and dates, filling in blank spaces with crosses to avoid allegations that notes were amended or added to later, and so on and so forth. It is also why Police Officers know that the very first thing you do when called to a crime scene is to interview the victims and witnesses immediately, and to create written records of what they said. Those records are going to be much more reliable than any document or statement that comes later.

Another instinct is this. In her pioneering and extremely controversial book Eye Witness Testimony, first published in 1979, criminal psychologist Elizabeth Loftus pointed out that the evidence of witnesses to events is mostly unintentionally fabricated. This rather alarming conclusion derives from the fact that particularly in events of trauma, such as violent or sexual crimes, the brain has a habit of intentionally erasing the most traumatic features of the incident and then replacing those memories with details that it makes up. And very unfortunately we lawyers know this to be true. That is why things like identity parades are so extremely unreliable, and things like body cameras are so valuable an innovation. Because while it is of course possible to fabricate videos, it is not nearly so easy to do so as it is for the human brain to make up details of what a person might have looked like, what they might have said, and what they might have done, amidst experiences of high stress or trauma. Eye witness testimony is basically very unreliable, and until a variety of recent technological advances - such as DNA testing, body cameras, ubiquitous high quality CCTV (CCTV used to be useless in legal trials, because it was all so fuzzy; now it is so exceptionally good that you can even identify a person through their retina) a lot of people were very sadly wrongfully convicted on the basis of eye witness testimony. This occurred through no necessary fault of the victims or the witnesses; this is how just how the human brain works in response to traumatic situations. The other result was low conviction rates in criminal trials, because juries instinctively understood this point and placed comparatively low weight on eye witness testimony.

Now we turn to the quasi-scientific art of cross-examination, the task of assessing the strength of a person's oral evidence in a court room by asking them a series of questions. This is an extremely challenging skill, and only the very best courtroom lawyers ever become masters at it. Although there are many books teaching a person how to conduct a cross-examination; and although there are many imagined rules to the art (e.g. "only ever ask closed questions, that is to say questions you already know the answer to" - so you are supposed to ask questions like "it was you who stabbed her with the knife, wasn't it?") the books don't in practice get you very far and neither do the rules. In fact the best cross-examinations are typically conducted entirely with open questions, quite contrary to the philosophy prevailing in the textbooks.

A conventional cross-examination theory proceeds by identifying inconsistencies between a witnesses's oral or written testimony and other materials or documents on the court file. A witness may have given testimony orally in court (this is common in US and English jury trials), by way of a written witness statement or in the form of a deposition (a series of question and answer sessions recorded and transcribed in front of the parties' lawyers without a Judge present, common in the United States and possible but rare in England). The documents on the file may include the testimony of other witnesses, or documents from a variety of sources (expert reports, emails, instant messaging records seized by the Police pursuant to a warrant, and so on and so forth). So the conventional method of cross-examination is to find an inconsistency in the documents, ask the witness a series of questions the witness will naturally agree to, and then terminate the line of questioning with a question that will cause the witness to contradict himself and appear either unreliable or a liar. For example:

You were in the Heartfelt Arms on the evening of Friday 13 July, weren't you?

- Yes, I was.

And then you walked home when the bar closed at 11.20, didn't you?

- Yes, that would have been right.

You didn't drive, did you? You'd been drinking alcohol.

- No, no I didn't.

It's about a 30 minute walk home, isn't it?

- Yes, that's right.

You walked straight home, didn't you?

- Yes, I did.

Now can I ask you to look at page 1284 of the bundle. That's an image of you on a CCTV camera, isn't it?

- Erm, yes, yes it is.

And the CCTV camera still shows it to be the CCTV camera on Kissing Street, doesn't it?

- Yes.

And the time shown on the CCTV camera is 00:40, isn't it?

- Oh erm oh err err ...

The problem with this sort of conventional line of cross-examination is that it doesn't work with well-prepared, intelligent and experienced witnesses, who will have had access to the court file and will spot where any particular line of cross-examination is going. And they will be ready with an answer to the final question, and it will not be "oh erm oh err err"; instead it will be some long complicated and plausible explanation that resolves all the inconsistencies and makes the witness look truthful and reasonable. In modern complex trials, witnesses are trained on how to survive cross-examination; they are trained to read the file; they are trained to spot lines of leading questions and where they are likely to be going; and their own lawyers highlight all the potential inconsistencies that might be drawn upon in cross-examination and they prepare the witnesses to give credible answers explaining the inconsistencies away (even if under the ethical systems of some legal professions, lawyers are not supposed to do this).

One method lawyers often use to prevent well-trained witnesses from evading the traps they have prepared in sophisticated lines of cross-examination is by badgering the witness, e.g. by saying "this is a question with a yes or no answer; please answer it yes or no". But this doesn't work. Firstly judges don't like it; secondly a well-trained witness will respond with words to the effect "I am sorry but to understand what actually happened I cannot just answer yes or no. I need to explain some context to you and then you will understand what really happened". So badgering or hectoring witnesses generally doesn't work.

To get around this problem, one unnerves the witness with a series of apparently unrelated open questions that do not have a natural cross-examination logic to them so that the witness does not know where the questions are leading. This is a real art; it requires in-depth research on the witness, often in relation to matters that have nothing to do with what the case is about; and it catches out liars. Instead of the series of questions above, consider the following:

Where did you go to school?

-- Err um err um what does that have to do with it?

Where did you go to school?

-- Heartfelt Grammar School.

While you were at school, did you have any criminal convictions?

-- No.

Are you sure?

-- Yes.

When you were at school, were you ever convicted for drink driving?

-- (Silence)

Where were you on the evening of Friday 13 July?

-- (Quiet voice) The Heartfelt Arms

How much did you have to drink?

-- Three or four pints.

Pints of weak beer, or of strong German lager?

-- Er er I don't remember.

What is the maximum alcohol blood content for driving a car in the United Kingdom?

-- Erm err erm I am not sure

You are not sure.

-- I am not sure.

In this way, the witness's credibility is completely destroyed and it really doesn't matter what the witness says in response to the rest of the questions asked. The effective lawyer has demolished the witness from the outset.

What does all this have to do with how to spot liars? The point is quite a simple one. When a person lies, they also prepare associated lies that corroborate the principal lie. If they say that they were somewhere at a certain time, they will manufacture details such as how they got there, who else was there, how they got home, what they were doing there, and so on and so forth.

However the truth is a web of facts more sophisticated and complex than any liar can manufacture. To spot a liar, all you need to do (if only it were that simple) is to think of areas of detail that might relate to the issue at hand that they have not thought of to manufacture; and to ask questions about those issues. Then the lying witness will trip up, but the truthful witness will survive the examination. Of course this exercise need not be undertaken in a courtroom; it applies in every area of life. However spotting liars reliably requires vast amounts of work. It involves extensive research into the individual under study, and then it requires huge preparation in preparing the right questions in the right order that will assist the examiner in getting to the bottom of whether the witness is telling the truth. It is this author's experience that as a lawyer, it takes between one and three hours of preparation, not including background research, to prepare for 15 to 20 minutes of cross-examination. And some cross-examinations go on for days, or even weeks. The art of getting to the truth is a monumental one.


bottom of page