Neuroscience and the Law

In 2009 when Brian Dugan pleaded guilty to the rape and murder of a female nurse, brain imaging was by the defense as evidence to suggest that Dugan may not have committed these crimes intentionally or that he was in a mental state that would somehow make him less personally responsible. An fMRI was discussed and interpreted in front a jury but the jury did not physically see the scans. In some other criminal cases, a polygraph has been used to tell if a witness or defendant is not being truthful in their testimony. Also, fMRI has shown that certain parts of the brain are more active than when a person is being honest, however, there is not a consensus on if this is true for every individual.

An fMRI includes a large magnet that measures the flow of oxygenated hemoglobin in the brain. When there is an influx in a certain area of the brain, the machine detects the signal using the magnet and in the brain image, the parts of the brain where there was increased flow are lit up. The image is not very spatially accurate though and nothing can be derived about individual neurons. Also, there is a lot of variability in brain activity from person to person within an experimental group, which makes it nearly impossible to make a definitive conclusion about the specific level functionality of one subject. A polygraph picks up electrical signals and detects arousal from the neurons in your peripheral nervous system and in the ones associated with emotion. Using this data, an investigator can try to conclude how honest the subject is being. Questions must be asked in such a way that the investigator does not use data conclusively from the subject that includes neuronal activity that may be associated with being nervous just from being investigated or hooked up to a machine.

Some professionals, mostly including defense attorneys, in the field of criminal law are in favor of being allowed to use fMRI scans, the most recent development in neuroscience that may be able to display an individual’s brain activity and mental state, in court as evidence. Although not with any certainty, an fMRI can reveal the mental state of an individual in the sense that the defendant may not be sane or is incapable of using rational thought or judgment based on the size of brain regions and the level of activity in regions associated with decision making, fear, emotion, etc. This would then lower the guilt of the suspect themselves. To some, this may allow for a more well-rounded assessment of the suspect, as the suspect would then be less personally guilty, and to the best of its ability, the law tries to measure the degree of responsibility one has for their previous actions.

The main point against using fMRI in court as evidence is that a recent scan is not reflective of the mental state of the suspect when they committed the crime, but rather the state when the scan was performed. For the scan to be relevant however, it would have to reveal something about the defendant when he was breaking the law. Also, individual scans cannot be compared accurately because this technology is only used in research to study groups of people because there is too much variation among individuals to gather meaningful conclusions. fMRI scanning is not established for diagnosis of any psychiatric disorders and the polygraph can be very inaccurate in detecting signal that solely indicate a lie and not something unrelated. Therefore, it is said that it should not be used to sway the jury’s decision because the scan may be falsely interpreted by the defense attorney.

Personally, I don’t think a polygraph or an fMRI should be used as evidence in court unless the image is taken very near the time of the crime and is compared with the scans of many other people who have committed the same crime and also with people who have similar scans. One image does not allow for a scientific or medical conclusion to be drawn about a subject, especially because although the data may seem very different from the average, the subject may very well be within statistical boundaries of the average. Every juror probably will not understand how to interpret statistics about that data presented and will not understand that the technology does not allow research scientists to declare anything about the mental state of person, especially when the defense attorney is not a scientist. Whether or not the person was mentally stable when they committed the crime or whether they could think rationally is not relevant to the consequences of their actions. If someone is murdered, whether or not the assailant is crazy doesn’t change the fact that the person is dead. The effect that the actions of the assailant had on society is what matters. Criminal law exists to protect the general public. The punishment for the crime should be proportional to the physical and definitive damage done, not whether or not they were mentally stable in the act.

3 responses to “Neuroscience and the Law”

  1. Brooke Nawrocki says:

    I also agree that it is necessary for the scan to have been taken around the time of the crime for it to hold up in court.

  2. Aiswarya Nagasubramony says:

    You have clearly pointed out why the fMRI and the polygraph should not be admissible in court yet. To be able to use this technology in court, these issues have to be sorted out.

  3. Aliya Saffran says:

    I agree that every juror will not be able to understand the technology and data that they are presented with. Unfortunately, I don’t know if this problem, in regards to neurotechnology could ever be completely solved.

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