Memory and the Law

Rebecca Fordham writes:

"Many experts are challenging the view that eyewitnesses recounting what they saw is the best way of tapping their memory. Some think brain scans could be the way forward." [Memory Mixup, BBC News Magazine, 17 June 2008]

We already have technology that is supposed to detect discrepancies between what the witness remembers and what the witness says - it's called a polygraph or lie detector. Now we apparently need another technology that detects discrepancies between what the witness consciously remembers and what is buried in the witness's unconscious.

The lie detector has been controversial ever since its invention, and features in a Chesterton story called "The Mistake of the Machine". (Of course it is not the machine that makes the mistake, as Chesterton's hero Father Brown points out, but the people using the machine who misinterpret its output.)

• Chesterton and Friends: Lie Detectors
• David Wallace-Wells: The Big Lie (Washington Monthly, April 2007), via AntiPolygraph.org
  

Of course humans sometimes lie, and sometimes this can be detected by the polygraph, but that doesn't make the polygraph an instrument of truth. (For that matter, people sometimes blurt out secrets under the influence of alcohol or torture, or get artistic inspiration under the influence of mind-bending drugs, but none of these are reliable instruments of truth either.)

And human memory is sometimes unreliable, but that doesn't make the brain scan an instrument of truth either. Constructing evidence from the unconscious contents of a brain is no more reliable than constructing history from an archaeological sift through a mediaeval rubbish tip. It may be possible, and may yield some intriguing results, but the results are always speculative and uncertain.

Meanwhile, our "common sense" understanding of the brain and its contents is probably less accurate and less coherent than our understanding of mediaeval waste disposal. That's why psychoanalysts make more money than archaeologists. They do, don't they?

Update

"India has become the first country to convict someone of a crime relying on evidence from this controversial machine." [Source: New York Times, via Bruce Schneier]

Shifting Standards

Bruce Schneier blogs about a retrospective drug test for athlete Lance Armstrong. It seems that blood samples are kept for many years, and may be subject to new tests.

"Athletes considering using banned substances [not only] have to evade any tests that exist today, [but also] have to at least think about how they could evade any tests that might be invented in the future."

Bruce suggests athletes need escrow blood samples, to defend themselves against retrospective charges.

Retrospective tests introduce new modes of risk and uncertainty for athletes. Not only new tests as Bruce indicates, but possibly also new interpretations of the regulations, based on shifting expert opinion from scientists and lawyers. (Does chemical substance X2 invented at time T2 and detected in a blood sample taken at time T3 count as banned under a regulation enacted at earlier time T1, which refers to an almost identical substance X1, if a reliable test to discriminate between X1 and X2 wasn't perfected until a later time T4, and X2 itself wasn't explicitly banned until T5? Complicated, huh?)

An older and long-established athlete may have access to more expensive ways of cheating, as well as a greater incentive to cheat as athletic prowess starts to wane. Meanwhile the direct cost of being detected (in terms of suspension from further competition) reduces to zero as the athletic career comes to an end. Retrospective testing may increase the chance of detection, but it also increases the average delay between transgression and detection. So we might expect retrospective testing to amplify the age imbalance: greater compliance from younger athletes, and lesser compliance from older ones.

Meanwhile, crime writer Patricia Cornwall has a theory (Portrait of a Killer) about the identity of Jack the Ripper, based partly on DNA evidence. (Nineteenth century crime subject to twentieth century forensics.) So do we also need to think of escrow DNA, to deal with posthumous allegations of crime or paternity?

[Update] Bruce Schneier adds some useful game theoretic analysis to his earlier post, prompted by dope-testing of Floyd Landis.

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