16 April 2022 | New Scientist | 35Truth and lies
The intriguing origin story behind the polygraph test should make
us worry about extending its use, says Chris Stokel-WalkerBook
Tremors in the Blood
Amit Katwala
Mudlark
THE polygraph test has been
used in criminal prosecutions for
decades – a silver bullet for police
and prosecutors alike. Measuring
heart rate, breathing speed and the
conductivity of skin, it is supposedly
infallible and given the respectable
veneer of science in a courtroom.
Someone who flunks the test must
be lying, their body’s tell-tale signs
betraying their deepest secrets.
Yet that is far from reality.
“There is no single tell-tale sign
of deception that holds true for
everyone – no Pinocchio’s nose,”
writes Amit Katwala in Tremors
in the Blood. A misfiring test has
real ramifications: the US-based
National Registry of Exonerations
holds records of more than
200 people who failed a polygraph
test, were convicted of a crime
and imprisoned, but were later
found to be innocent.
Katwala’s book traces the
test’s history, looking at the early
adopters of the technology and
some of its earliest cases. The book
goes back a century, telling the story
of John Larson and Leonarde Keeler,
co-inventors of the polygraph
(called the emotograph by Keeler),
and August Vollmer – all three key
to its adoption by US police forces
and later worldwide.
Larson was a complex character,
breathed back to life by Katwala’s
meticulous research. A bookish,
morally driven individual, Larson
joined the Californian police force
in the early 1920s. Unlike the high
school dropouts and extortionists
who filled the force’s ranks then,
Larson was the only police officer in
the US with a PhD, in physiology. He
would work in university labs by day
and police the streets at night.
Larson’s master’s thesis had been
on the relatively new technology of
fingerprint identification, which had
recently become admissible in court.
He thought there were still more
ways of catching criminals. He was
lucky to work under a police chief,
Vollmer, who was more bookish
than he liked to let on.
Vollmer was equally driven to do
the right thing, and was constantly
trying to improve policing. In 1921,
after reading an academic paper by
a psychologist and lawyer who had
tested whether his friends were
lying based on their blood pressure
readings, Vollmer asked Larson
to develop a machine that could
do the same. The result was mocked
by fellow officers, and described
in newspapers as looking like a
combination of radio, gas stove,
stethoscope, dentist’s drill,
barometer, wind gauge, time ball
(an old form of clock) and watch –
but it appeared to work.
Katwala vividly portrays
those heady early days when the
polygraph seemed to catch out
liars. Then, he deftly delivers thetwist in the tale: 40-odd years after
cobbling together the first machine,
Larson forswore his invention
because of the way it was used.
It was “nothing more than a
psychological third degree aimed
at extorting confessions, as the old
physical beatings were”, he said in
an interview – far removed from his
meticulous scientific approach.
The book captures the wonder of
scientific breakthrough – and what
happens as the story becomes more
complex. In 1965, the year Larson
died, the US House Committee on
Government Operations warned that
the world had been hoodwinked
by “a myth that a metal box in the
hands of an investigator can detect
truth or falsehood”.
Yet the polygraph is still being
used. In 2021, the UK began
polygraph testing people convicted
of terrorism offences and, later that
year, convicted domestic abusers,
despite the fact there are serious
doubts about whether it works.
Why has the polygraph remained
on its pedestal? Perhaps because
no one, until now, has placed it,
warts and all, in its historical and
scientific context. ❚Chris Stokel-Walker is a journalist
based in Newcastle, UKThe polygraph test looked
scientific because it was based
on physiological readingsPE
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