If a brain can be caught lying, should we admit that evidence to court? Here’s what legal experts think.
A man is charged with stealing a very distinctive blue diamond. The man claims never to have seen the diamond before. An expert is called to testify whether the brain responses exhibited by this man indicate he has seen the diamond before. The question is – should this information be used in court?
Courts are reluctant to admit evidence where there is considerable debate over the interpretation of scientific findings. But a recent study from researchers in the US has noted that the accuracy of such “mind reading” technology is improving.
There are various methods of detecting false statements or concealed knowledge, which vary greatly. For example, traditional “lie detection” relies on measuring physiological reactions such as heart rate, blood pressure, pupil dilation and skin sweat response to direct questions, such as “did you kill your wife?” Alternatively, a functional magnetic resonance imaging (fMRI) approach uses brain scans to identify a brain signature for lying.
However, the technology considered by the US researchers, known as “brain fingerprinting”, “guilty knowledge tests” or “concealed information tests”, differs from standard lie detection because it claims to reveal the fingerprint of knowledge stored in the brain. For example, in the case of the hypothetical blue diamond, knowledge of what type of diamond was stolen, where it was stolen, and what type of tools were used to effect the theft.
This technique gathers electrical signals within the brain through the scalp by electroencephalography (EEG), signals which indicate brain responses. Known as the P300 signal, those responses to questions or visual stimuli are assessed for signs that the individual recognises certain pieces of information. The process includes some questions that are neutral in content and used as controls, while others probe for knowledge of facts related to the offence.
The P300 response typically occurs some 300 to 800 milliseconds after the stimulus, and it is said that those tested will react to the stimulus before they are able to conceal their response. If the probes sufficiently narrow the focus to knowledge that only the perpetrator of the crime could possess, then the test is said to be “accurate” in revealing this concealed knowledge. Proponents of the use of this technology argue that this gives much stronger evidence than is possible to get through human assessment.
Memory detection technologies are improving, but even if they are “accurate” (however we choose to define that term) it does not automatically mean they will or should be allowed in court. Society, legislators and the courts are going to have to decide whether our memories should be allowed to remain private or whether the needs of justice trump privacy considerations. Our innermost thoughts have always been viewed as private; are we ready to surrender them to law enforcement agencies?