At Northwestern University in Illinois, a group of psychologists are teaching students how to commit the perfect crime.
They are taught how to break into a small office on the university campus, told the location of valuables belonging to members of staff – including a silver ring – and tipped off about the best time to strike to avoid being caught. Later this day, each of these students will effectively become a thief.
Of course this ‘crime’ is entirely staged. What interests the psychologists is how the human brain controls the memories stored from participating in criminal acts, and the extent to which they can be hidden. The mock crime scenarios should help – and the findings could have implications for some criminal cases being heard right now.
The working assumption is that a new generation of tests based on brain scans are less fallible than traditional lie tests
“For years people have assumed that when a criminal is presented with a reminder of their deeds, the brain will automatically elicit this recognition component,” says Zara Bergstrom, a psychologist at the University of Kent involved in the study. “But no one’s seriously questioned if this is true. Can people stop their mind remembering something they don’t want to think about, and if so how does this happen?”
The very fact that these questions are still open for research could be seen as worrying. Over the past decade, neuroscience has moved from the laboratory into law enforcement systems and courtrooms across the world. And while it’s reasonably well known that traditional lie-detection tests – polygraphs – are unreliable, the working assumption is that a new generation of tests based on brain scans are less fallible. Trust in the technology is so high, in fact, that it is already playing an important role in separating the guilty from the innocent, particularly in India.
In 2008, 24-year-old business student Aditi Sharma was jailed for life for poisoning her former fiance Udit Bharati with sweets dipped in arsenic. Bharati had been angry after Sharma broke off their engagement to be with another man.
Brain fingerprinting has been used by police in India since 2003
While Sharma protested her innocence in court, Judge Shalini Pransalkar Joshi had little doubt. During sentencing, she explained that the brain scan conducted on Sharma appeared to show that she had “experiential knowledge” of arsenic, the murder itself and the way Bharati was killed.
Police in India have used brain fingerprinting since 2003. Officers argue that it helps an overloaded workforce augment their evidence and speed up the often tortuously drawn-out process of conviction.
The approach typically involves asking the accused to sit silently in a small, windowless room, while listening to a tape playing a series of statements – some of which are associated with the crime. A skullcap with a set of 30 electrodes detects their brain activity, and feeds the information back to an electro-encephalograph (EEG) machine. Some neuroscientists believe this reveals whether the suspect shows prior knowledge of a particular cue – a murder weapon, for example, or the injuries suffered by a victim.
At the heart of the brain fingerprinting test is the search for a particular electrical signal emitted by the brain. It’s called the P300. This signal becomes noticeably larger when someone receives verbal or visual cues regarding objects, people or locations associated with an especially vivid and emotionally charged memory.
Brain fingerprinting searches for a particular brain signal called the P300
The relationship between the P300 and recognition was first discovered by neuroscientists in the mid 1960s. They found a consistent surge of electrical activity in the brain, occurring around 300 milliseconds after a cue – such as seeing a relative’s photograph. But it would be another 30 years before anyone attempted to exploit the P300 for solving crimes.