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YOU have just been arrested on suspicion of murder. You’re sweating it out in
the interrogation room with a pair of beefy detectives. But your lips are
sealed—you know your rights.

Then with a smirk they slip a thing like a hairnet covered in dozens of tiny
electrodes over your head and sit you down in front of a computer. Pictures of
the crime scene begin to flash up on the screen interspersed with
multiple-choice questions. Flash! A photo of a brick wall. Flash! “What lies
behind this wall?” Flash! “Cement and blacktop?” Flash! “Sand and gravel?”
Flash! “Weeds and grass?”

You said nothing. You were even trying not to think. But sorry buddy, your
brain just gave you away. It couldn’t help but show an electrical start of
recognition at the image matching the memory of hurdling a wall and wading
through a backyard of weeds as you fled.

An Orwellian fantasy? No, this technique was actually used in a recent test
case at a County Court in Iowa. The brain reading technology was developed in
university labs with CIA money. And it’s not the only way that researchers are
searching for new ways to probe a lying mind. The US Department of Defense is
funding research into the use of multimillion dollar brain scanners. Other labs
are looking at more low-tech methods, such as a simple reaction time test that
can be an astonishingly reliable way of discovering “guilty knowledge” you might
rather conceal.

The field of lie detecting is long overdue for a shake-up. The polygraph is
still hugely controversial, based as it is on emotional responses such as sweaty
palms and changes in blood pressure or breathing patterns. Polygraph results can
be offered as evidence for the defence in US courts, and the American Civil
Liberties Union estimates that more than a million tests are performed each
year. But many people believe the polygraph is unreliable—the Internet
will tell you how to fool the machine by clenching your buttocks or biting your
tongue. However, the test is still widely used by security forces in the US,
Israel and Japan. In the US, the FBI and CIA screen potential employees, and the
US government is even pushing through the polygraph for scientists working at
national research labs.

But what if you could get inside someone’s head? Forget about easy-to-fake
emotional responses. Just look for the differences in brain signals that reveal
when someone is lying, or even probe directly for the information they’re trying
to conceal. Believe it or not, brain researchers can already do this with
startling accuracy.

It all began in the early 1990s when the CIA gave a little money to Emanuel
Donchin, a psychologist at the University of Illinois, Urbana-Champaign, and his
student, Lawrence Farwell, to see what they could do with an EEG test. The EEG,
or electroencephalograph, uses super-sensitive electrodes to measure
fluctuations in electrical potential caused by patterns of brain activity.
Donchin is an expert on a particular characteristic bump in the EEG trace called
the P300, which happens about a third of a second after you notice something
significant. It’s like a mental click of recognition. Crucially, it’s automatic
and utterly predictable.

How would the P300 expose a lie? There are two ways of using a polygraph. The
standard way is to first ask a stressful, but general, question like “Have you
ever driven while slightly over the limit?” This creates a baseline reading
before you jump in with the serious questions such as “Have you had unauthorised
contact with a foreign national?” The rationale is that only guilty people will
react strongly to actual accusations. It is of course the ease with which the
knowledgeable can pump up their arousal during the baseline readings, disguising
any later lies, which has brought the polygraph into such disrepute.

But there is an alternative, little-used form of testing, known as the
“guilty knowledge test”. Subjects are probed with pictures or phrases
significant only to them. A suspected KGB agent might have been tested for an
emotional reaction—such as a skip of the heart or ragged
breathing—to KGB code words. A suspected criminal would be tested for
knowledge of a particular crime.

Donchin and Farwell realised that the guilty knowledge test dovetailed neatly
with P300 recording. People with secret knowledge should show a P300 to
otherwise innocent-looking pictures or phrases. They set up a lab test in which
subjects had to play-act spy scenarios—fictitious missions like delivering
the “owl file” to a contact in a blue coat in a particular street. Then they
recorded brain responses to lists of words which included innocuous alternatives
like the “fog file” and a contact in a red scarf. Analysis of P300 responses
picked out nearly 90 per cent of the “spies”. More importantly, there were no
false positives where “guilty” brain waves betrayed innocent people.

Although the researchers published their findings in 1991 in the journal
Psychophysiology, nothing much more happened until this year when a hearing at
Pottawattamie County Court in the backwoods of Iowa suddenly grabbed
international headlines. Someone was trying to use P300 evidence to get a
convicted murderer released.

Terry Harrington was jailed for life in 1978 for shooting a security guard in
the street. Harrington was just 17 at the time and claimed he’d been miles away
at a pop concert. But he was convicted on the testimony of several witnesses,
some allegedly his accomplices, and forensic evidence including gunpowder traces
found on his jacket. In a bid to win the right to appeal, Harrington came to
court to show that his brain did not react to any memories of the crime scene
but responded strongly to phrases connected with events at the concert.

The scientist running the EEG tests was Farwell, who’d set up shop in Iowa in
the hope of turning the P300 research into a business. Farwell had quietly spent
the 1990s working with the CIA and the FBI trying to prove his technology in the
field. If Pottawattamie County Court could be persuaded to accept his methods in
this test case, he expected to revolutionise the whole field of crime
fighting.

“In a criminal act, there may or may not be many kinds of peripheral
evidence, but the brain is always there, planning, executing, and recording the
crime,” says Farwell. “The fundamental difference between a perpetrator and a
falsely accused, innocent person is that the perpetrator, having committed the
crime, has the details of the crime stored in his brain, and the innocent
suspect does not.”

Farwell’s dream is that EEG testing, which he has dubbed Brain
Fingerprinting, will become a painless way of eliminating innocent people as
well as fingering crooks in any investigation. He says if every police station
had the right gear, suspects could volunteer to take the guilty knowledge test
and perhaps clear their name.

He claims his Brain Fingerprinting is foolproof if performed right. People
can disrupt the recording by blinking or refusing to look at the words. But they
cannot cheat to produce a false reading. Farwell says that he tried it out on a
psychopathic serial killer, whose lack of emotions would have been a disaster
for any polygraph test. “This guy never showed much of any kind of emotion. He
certainly wasn’t normal. But I got a big Brain Fingerprint response to facts
about a murder,” he says. “This method taps straight into the cognitive
processes of the brain and doesn’t rely on an emotional reaction.”

When it came to the Harrington case, there were immense difficulties because
the murder happened more than 20 years ago, so Harrington’s memories were hardly
fresh. Farwell also had to find details related to the murder which a court
could believe that Harrington had not learned during the original trial or in
the many years since. Poring over old court transcripts and visiting the crime
scene, Farwell felt that they could use the route the guard’s killer must have
taken as he ran away which involved jumping a ditch and crossing a weedy plot.
When Farwell ran the tests, Harrington indeed showed no P300 to these details,
and a clear response to details about the concert which was his alibi.

A cut and dried case? Unfortunately for Farwell and Harrington, it does not
seem so. In court, expert witnesses, including Farwell’s old professor Donchin,
said the procedure was still too much of an unknown art, even though the science
was certainly sound. District attorney Rick Crowl scoffed at Farwell’s claims
that there was a deep ditch at the time or that weeds would have been that
memorable in the rush to escape. Harrington’s positive response to the alibi
details would simply have come from rehearsing his story for so many years.

Farwell himself came under attack. Fun was made of the fact that he taught
Kung Fu and had said he was on the faculty of Harvard Medical School (Farwell
admitted this consisted of some brief consultancy work).

In March, the judge eventually refused Harrington leave to appeal. Farwell
says he is saddened, but at least he presented his Brain Fingerprinting evidence
before a judge, which sets a precedent for its use in future hearings. Are we
going to see a Brain Fingerprinting technician in every police station? That’s
not likely to happen any time soon according to other people at the trial,
including district attorney Crowl.

The difficulty isn’t the equipment, which is no more technically demanding
than the polygraph. Instead, it has more to do with the culture of interrogation
which prefers to see someone sweat. Cynics say the polygraph is used purely to
intimidate suspects. The aim is to prove the machine cannot be fooled, making
people think they have no hope of escape and so confess. Any approach that would
extract answers from a subject’s mind in a detached and clinical way wouldn’t
have the same effect.

But this isn’t slowing the researchers down. Studies of what characterises a
lying brain are suddenly abundant. At the high-tech end of the market, the US
Department of Defense is funding Stephen Kosslyn, a psychologist at Harvard
University, to do magnetic resonance brain imaging studies. Kosslyn says his
first results are not that encouraging. People’s brain activity seems to be far
from consistent when they are lying—but it is early days.

At least half a dozen other US labs are working on EEG measures. Perhaps the
most successful is Peter Rosenfeld from Northwestern University in Illinois.
Whereas Farwell’s technique depends on a guilty knowledge test that shows
whether a person has a memory for a particular fact, Rosenfeld has recently
discovered a detectable distortion in the P300 signal just because you need to
concentrate when telling a lie.

In Rosenfeld’s experiment a subject’s own year of birth slipped into a random
series of four figure numbers was enough to produce a bump of recognition in the
P300. Some volunteers were instructed to answer “no” when asked if they had seen
it. When they lied there was a distinctive pattern in the way the strength of
P300 signal was distributed across the scalp. Rosenfeld says he hopes EEG tests
will both reveal guilty knowledge and whether people are trying to lie during an
interrogation.

And then taking everyone by surprise was the publication in February of a
low-tech version of the guilty knowledge test which needs no scanner or
electrodes, but just measures reaction times. Travis Seymour and Colleen Seifert
from the University of Michigan, Ann Arbor, repeated exactly the same spy
scenario as Donchin and Farwell, but they simply looked for hesitations in the
subjects’ answers.

Seymour says they found that those who were telling the truth about a phrase
being unfamiliar could hit the “no” button in half a second. But people telling
a lie took more like a second. Even if they knew what was giving them away and
given a chance to practise, they could not react any faster. “This seems a
super-cheap and easy way of doing the guilty knowledge test,” says Seymour. “All
you need is an ordinary PC and a keyboard. No electrodes.” However, he adds that
it would require much more work to take such lab demonstrations further.

Rosenfeld agrees, saying researchers have been surprised at what you can do
in the lab but no one is doing the extra work to prove the techniques would be
safe for the interrogation room. Even if the scientists do a good job on the
test protocols, he feels that won’t stop brain wave and reaction time technology
being abused just like the polygraph. He says the FBI knows that the polygraph
is unreliable. But they still value it as a prop because people can easily be
frightened into confessing if they believe the machine is reading their every
emotion. How much better a prop would a set of electrodes and a box of expensive
electronics make? The scientific validity of brain measures would be almost
beside the point.

And yet there seems real potential in the recent EEG work. Civil rights
activists take note. Tomorrow we may still enjoy the right to remain silent. But
that might be pointless if the investigator can read your mind.