Brain wave may help investigate crimes: study

Brain activity can be used to tell whether someone recognises details they encountered in normal, daily life, which may have implications for criminal investigations and use in courtrooms, new research shows.
The findings suggest that a particular brain wave, known as P300, could serve as a marker that identifies places, objects, or other details that a person has seen and recognises from everyday life.
Research using Electroencephalography (EEG) recordings of brain activity has shown that the P300 brain wave tends to be large when a person recognises a meaningful item among a list of non-meaningful items.
Using P300, researchers can give a subject a test called the Concealed Information Test (CIT) to try to determine whether they recognise information that is related to a crime or other event.

The study marks an important advance, said lead research John B Meixner of Northwestern University, because it draws on details from activities in participants' normal, daily lives.
"Much like a real crime, our participants made their own decisions and were exposed to all of the distracting information in the world," he said.

"Perhaps the most surprising finding was the extent to which we could detect very trivial details from a subject's day, such as the colour of umbrella that the participant had used," said Meixner.
Meixner and co-author J Peter Rosenfeld fitted 24 college student participants with small cameras that recorded both video and sound - the students wore the cameras clipped to their clothes for 4 hours as they went about their day.

For half of the students, the researchers used the recordings to identify details specific to each person's day, which became "probe" items for that person.
The researchers also came up with corresponding, "irrelevant" items that the student had not encountered.
For the other half of the students, the "probe" items related to details or items they had not encountered, but which were instead drawn from the recordings of other participants.
The next day, all of the students returned to the lab and were shown a series of words that described different details or items (ie, the probe and irrelevant items), while their brain activity was recorded via EEG.

The results showed that the P300 was larger for probe items than for irrelevant items, but only for the students who had actually seen or encountered the probe.
Further analyses showed that P300 responses effectively distinguished probe items from irrelevant items on the level of each individual participant, suggesting that it is a robust and reliable marker of recognition.
These findings have implications for memory research, but they may also have real-world application in the domain of criminal law, researchers said.
The study was published in the journal Psychological Science.