The points against permanent implanted monitoring are compelling: it is a considerable conceptual and legal step to go from external surveillance to the direct constant observation of the brain; it pre-empts a future crime rather than preventing crime in progress, and this involves an element of prejudging the subject; once deployed in this way the technology will inevitably spread to other uses, and the consequences of those should also be considered; and finally and most significantly, such a device entails the possibility of real-time correction of recidivist brain function, and this being arguably a form of mind control is ethically repellent to many. There is an instinctual argument, with respectable intellectual backing, that the System and the Witness should monitor the external world only, and the boundary of the body should be respected until there is a specific reason to do otherwise—as in a non-consensual interview—and even then such interference should be as brief as possible, and proportionate.