Lie Detector Technology in court – seduced by neuroscience?

Jeffrey Bellin from the California Courts of Appeal has a paper forthcoming in Temple Law Review on the legal issues involved in deploying new lie detection technology – specifically fMRI technology – in real-world courtroom settings (hat tip to the Neuroethics and Law blog ).

Bellin examines the ‘scientific validity’ requirements and argues that the research has progressed to the point where fMRI evidence in deception detection issues will soon reach the standard required to be admissible under the Daubert criteria. However, Bellin’s key issue with using fMRI evidence in court is not on scientific but on legal grounds: he claims that fMRI evidence would fall foul of the hearsay prohibition. He explains that “The hearsay problem arises because lie detector evidence consists of expert analysis of out-of-court statements offered for their truth (i.e., hearsay) and is consequently inadmissible under Federal Rule of Evidence 801 absent an applicable hearsay exception” (p.102).

I am not a lawyer so can’t really comment on the hearsay issue raised by Bellin, except to say that it’s an interesting observation and not one I’ve heard before. I feel better placed to assess his analysis that fMRI technology is only a small step from reaching the Daubert standard. In this Bellin is – in my judgement – way off-beam. His argument runs something like this:

1. The US Government has poured lots of money into lie detection techologies (Bellin quotes a Time magazine guess-timate of “tens of millions to hundreds of millions of dollars” – an uncorroborated rumour, not an established fact).

2. fMRI is “the most promising of the emerging new lie detection technologies” (p.106) because “brain activities will be more difficult to suppress than typical stress reactions measured by traditional polygraph examinations, [so] new technologies like fMRI show great promise for the development of scientifically valid lie detectors” (p.106).

3. Thus, “The infusion of money and energy into the science of lie detection coupled with the pace of recent developments in that science suggest that it is only a matter of time before lie detector evidence meets the Daubert threshold for scientific validity.” (p.107).

And the references he provides for this analysis? Steve Silberman’s “Don’t Even Think About Lying” in Wired Magazine from 2006, a piece in Time magazine the same year, entitled “How to Spot a Liar“, by Jeffrey Kluger and Coco Masters. Now both of these articles are fine pieces of journalism, but they hardly constitute good grounds for Bellin’s assertion that fMRI techology is almost ready to be admitted in court. (And if you’re going to use journalistic pieces as references, can I recommend, as a much better source, an excellent article: “Duped: Can brain scans uncover lies?” by Margaret Talbot from The New Yorker [July 2, 2007].)

Let’s just remind ourselves of the Daubert criteria. To paraphrase the comprehensive Wikipedia page, before expert testimony can be entered into evidence it must be relevant to the case at hand, and the expert’s conclusions must be scientific. This latter condition means that a judge deciding on whether to admit expert testimony based on a technique has to address five points:

1. Has the technique been tested in actual field conditions (and not just in a laboratory)?
2. Has the technique been subject to peer review and publication?
3. What is the known or potential rate of error? Is it zero, or low enough to be close to zero?
4. Do standards exist for the control of the technique’s operation?
5. Has the technique been generally accepted within the relevant scientific community?

As far as fMRI for lie detection is concerned I think the answers are:

  1. No, with only a couple of exceptions.
  2. Yes, though there is a long way to go before the technique has been tested in relevant conditions.
  3. In some lab conditions, accuracy rates reach 95%. But what about in real life situations? We don’t have enough research to say.
  4. There are no published or agreed standards for undertaking deception detection fMRI scans.
  5. No, the arguments are still raging!

As an example of 5, one of the crucial arguments is over the interpretation of the results of fMRI experiments (Logothetis, 2008). Mind Hacks had a terrific article a few weeks ago in which they summarise the key issue:

It starts with this simple question: what is fMRI measuring? When we talk about imaging experiments, we usually say it measures ‘brain activity’, but you may be surprised to know that no-one’s really sure what this actually means.

And as Jonah Lehrer points out more recently :

[...T]he critical flaw of such studies is that they neglect the vast interconnectivity of the brain… Because large swaths of the cortex are involved in almost every aspect of cognition – even a mind at rest exhibits widespread neural activity – the typical fMRI image, with its highly localized spots of color, can be deceptive. The technology makes sense of the mind by leaving lots of stuff out – it attempts to sort the “noise” from the “signal” – but sometimes what’s left out is essential to understanding what’s really going on.

Bellin is not alone in perhaps being seduced by the fMRI myth, as two recent studies (McCabe & Castel, 2007; Wiesberg et al., 2008) demonstrate very nicely. McCabe and Castel showed that participants judged news stories as ‘more scientific’ when accompanied by images of brain scans than without, and Weisberg et al.’s participants rated bad explanations of psychological phenomena as more scientifically sound when they included a spurious neuroscience reference. Why are people so beguiled by the blobs in the brain? Here are McCabe and Castel, quoted in the BPS Research Blog:

McCabe and Castel said their results show people have a “natural affinity for reductionistic explanations of cognitive phenomena, such that physical representations of cognitive processes, like brain images, are more satisfying, or more credible, than more abstract representations, like tables or bar graphs.”


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