Skip to main content

Neural Prosthetics, Behavior Control and Criminal Responsibility

By Walter Glannon, PhD

Walter Glannon is a professor of philosophy at the University of Calgary where he holds the Canada Research Chair in Biomedical Ethics and Ethical Theory. He is also a member of the AJOB Neuroscience editorial board.

Philosophers have argued that moral and criminal responsibility presuppose that actions cannot result from sequences that bypass agents’ control of their mental states as the causes of their actions (A. Mele, Autonomous Agents, 1995). Agents must act from their own mechanisms, which cannot be influenced by drugs, electrical stimulation of the brain, brainwashing or other interventions (J. M. Fischer and M. Ravizza, Responsibility and Control, 1998). Moral and criminal responsibility excludes all forms of brain manipulation.


With deep-brain stimulation (DBS) and brain-computer interfaces (BCIs), neuroscientists can alter the brain and the mental capacities it mediates. The first device modulates dysfunctional neural circuits causing neurological and psychiatric disorders through electrical stimulation of targeted sites in the brain. The second allows people with extensive paralysis to bypass the site of injury and translate intentions into actions by transmitting signals from the motor cortex to a computer. Because these devices and the practitioners who implant and activate them manipulate the brain and mind, the philosophical argument noted above suggests that they undermine the mental control necessary for criminal responsibility. Yet by modulating, bypassing or replacing damaged or dysfunctional regions of the brain, they can restore the mental capacities necessary to form and execute action plans. By enabling rather than disabling these capacities, neural prosthetics allow people to regain enough control of their thought and behavior to act autonomously and be responsible for their actions. Moral and criminal responsibility does not depend on brain function or dysfunction as such but on whether or to what extent the brain enables or impairs the mental capacities necessary for behavior control. In cases of brain injury or disease impairing these capacities, brain implants may restore some of this control. Theoretically, it does not matter whether mental states and events are generated and sustained by a natural or artificial system, provided that agents identify these states and events as their own and is what moves them to action. Artificial devices implanted to regulate thought and behavior are not necessarily alien to the agent but can be considered as a type of expanded embodiment. They can ensure that the agent is the source of her actions. Brain- and mind-altering devices should make us reconsider the meaning of ‘autonomy,’ ‘ownership’ and ‘control’ in discussions of moral and criminal responsibility.

To be criminally responsible for an action, an agent must have the requisite mens rea (“guilty mind”) and perform the requisite actus reus (“bad act”). According to the first criterion, the agent acts with the appropriate mental states corresponding to the definition of the criminal offense. These include intention, knowledge, negligence or recklessness. According to the second criterion, the agent voluntarily performs an intentional bodily movement in committing the offense. The agent’s mental states explain the action insofar as they cause it, and thus the mental basis of responsibility is distinct from the physical content of responsibility, what one is responsible for. Some neural prosthetics should also make us reconsider the relationship between mens rea and actus reus and the distinction between the mental basis and the physical content of responsibility. With these devices, what an agent is criminally responsible for might not be a bodily movement but a mental act. For example, a severely paralyzed subject using a BCI cannot perform any bodily movement and has to plan how he will move a robotic arm or computer cursor in translating his intention from electrodes placed on his scalp or implanted in his motor cortex to a computer. His execution of the intention is a mental act and is something for which he could be criminally responsible. Suppose that the subject is frustrated with the slow pace at which he is learning how to operate the robotic arm but is adept enough in operating it to assault the practitioner training him. In this case, there is no bodily movement but a mental act of executing an intention to move the robotic arm in a certain way. The execution of the intention is not the cause of the guilty act but is the guilty act itself. While the agent is also responsible for moving the robotic arm, this is not the only event for which he is responsible. The assault with the robotic arm could even be described as the consequence of his mental act that is the actus reus.

Via Buchen 2012

Neural prosthetics may also generate obligations that do not apply to people with normal brain function. Suppose that a person with a DBS system implanted in his brain is able to turn off the stimulator. This could cause a return of motor symptoms in a neurological disorder or affective and cognitive symptoms in a psychiatric disorder. In both cases, the decision to turn off the stimulator could cause the person to lose control of her thought and behavior. If she committed a criminal act while incapacitated, then she could be criminally responsible for the action on grounds of negligence or recklessness in foreseeing but ignoring the risks of deactivating the device. The agent failed to discharge her obligation to keep the stimulator on. In some respects, this is similar to being criminally responsible for injuring a pedestrian while driving under the influence of alcohol. But what is different in this case is that having the device in one’s brain seems to generate an obligation to keep it on at all times, an obligation generated by a disease over which the individual had no control.

In sum, there are at least three respects in which neural prosthetics should make us reassess how we think of responsibility and obligation. They challenge the view that manipulation of the brain and mind always undermines the control necessary for responsibility and recommend a broader interpretation of autonomous agency. By including mental acts in the content of responsibility, they also raise questions about the distinction between mens rea and actus reus as a mental-physical distinction and the identification of a guilty act as a bodily movement. And they may generate obligations regarding behavior control that people with devices implanted in their brains would not have had but for a neurological or psychiatric disorder.

Want to cite this post?

Glannon, W. (2014). Neural Prosthetics, Behavior Control and Criminal Responsibility. The Neuroethics Blog. Retrieved on
, from


Emory Neuroethics on Facebook