A brain wave linked to memory may be a telltale marker for criminal investigators, divulging when a person under scrutiny knows a damning morsel of knowledge — such as the weapon used to commit a murder, according to a new study from Northwestern University.
The findings, posted Tuesday at the Association for Psychological Science website, center on a unique, brain-emitted electrical signal called the P300. Scalp-affixed electrodes show that P300 waves become measurably larger in people as they are asked about then recognize specific items, people or locations that they've personally seen or experienced, perhaps offering detectives a next-generation tool for cracking cases, researchers assert.
Such wave-reading tests — sort of a polygraph 2.0 — are likely years from being allowed as evidence offered to American juries, if ever. But Japanese law enforcement officers already administer — more than 5,000 times a year — a rudimentary form of that exam called the Concealed Information Test (CIT), which is crafted to sniff out a person’s "guilty" insight into a crime, according to the FBI. (Traditional polygraph tests, which track changes in pulse and respiration during interrogations, remain blocked from U.S. criminal courts.)
“Regardless of whether the (CIT) test is admissible in court, it could still be used by police forces as an investigation tool,” said John B. Meixner, co-author of the Northwestern study and a law clerk for Chief U.S. District Judge Gerald Rosen in Michigan.
“This study is important because we demonstrate that the CIT can be effective in detecting information about real-world events,” Meixner said. “American police have shown little interest in using the CIT to date. This is unfortunate because the CIT is highly accurate and rarely has a false positive … typically less than 5 percent of the time. This is in contrast with the more-often used polygraph ‘lie detector’ test, which has a higher false-positive rate."
To conduct the experiments - and push the bounds of traditional CIT methods - researchers clipped small cameras to the clothing of 24 study participants (all college students), recording the sights and sounds of one day. The scientists later reviewed the footage and selected tangible tidbits: a red umbrella one carried; the chat another had with a person named Steve; the physics class a third attended; and the sandwich a fourth student ate at Subway shop.
The next day, the students returned to a lab and were fitted with electroencephalography (EEG) sensors on their heads as researchers sought to replicate a police investigation — quizzing them about details from their previous days as if they were suspects with knowledge of a crime.
Half of the participants were purposely shown words mentioning objects or people they had not encountered. Their P300 waves remained consistently small. The others were shown words reflecting items or individuals they had seen — causing their P300 waves to grow larger, researchers noted.
In a real-world investigation, the umbrella could have been a .357 Magnum gun, “Steve” could have been an accomplice, and the larger brain waves could have hinted at a guilty conscience, Meixner said.
“It's important to note, (however), that recognition does not necessarily imply guilt,” Meixner added. “If I recognize the murder weapon, that could mean any number of things: perhaps I'm a friend of the guilty party and I know what gun he owns; or maybe I sold that gun to a suspect days before; or, perhaps that type of gun is meaningful to me for some other totally random reason — maybe my best friend was shot using that type of gun.
“The CIT can't tell you any of this — it’s up to the police, or potentially a judge or jury, to interpret what the recognition means,” he added.
Some U.S. law enforcement experts recently backed an increased use of the CIT as an investigatory tool — even before the brain-wave connection was made at Northwestern.
“The Concealed Information Test detects a person’s guilty knowledge of a crime, unlike the traditional polygraph … test that assesses deception to direct, accusatory questions. Investigators (who use CIT) analyze crime scene evidence to identify items most likely to be memorable and important to the offender. Extensive use of the CIT by Japanese investigators is indicative of its effectiveness," Blake McConnell, a retired FBI special agent, and Timothy J. Weber, an ex-federal polygraph instructor, co-wrote in the August issue of the FBI Law Enforcement Bulletin.
To many cops, the CIT already was considered a better form of the polygraph — “but from the 22nd century,” said Keith Sullivan, an attorney and partner with Sullivan & Galleshaw, a New York City law firm.
“We know so little about the brain and its operation — and this type of testing is advancing those studies in leaps and bounds,” Sullivan said.
“The day will come,” he predicted, “where CIT test results will be used in a criminal case, perhaps to show familiarity with a known accomplice or victim or unknown facts of a case.”