A guilty conscience can be a hard burden to bear, but not one that can convict someone… until now. Neural imaging is reaching the point where it can be used to determine if someone has committed a crime, although its reliability and legal standing is still up for debate.

The idea of using functional magnetic resonance imaging (fMRI) to determine guilt involves detecting changes in blood flow, which highlights active parts of the brain. Like with lie detectors, certain areas of the brain light up when someone is lying, while others light up when they tell the truth. They can detect when a person is lying with 70 to 90 percent accuracy, which is pretty good, but still lacks complete accuracy.

Brain scans can also be used to detect if someone recognizes an image, such as the scene of a crime or a stolen item. However, that is also somewhat unreliable, since they may show the same signs if the person being scanned merely imagines committing the crime based off the scene, or has been to a location before separate from the crime.

Furthermore, there are legal questions involved in using brain scans to determine guilt. This is a new area, so it’s hard to apply existing privacy laws to this, although one would like to think that their brainwaves are their own business, and should be able to consent to a scan before being subjected to one.

Of course, like any other way of detecting guilt, there are ways people can try to defeat it. There will always be those who find ways to work around the system, by thinking completely random thoughts or just remaining so composed and lying to themselves so well they believe their own stories. It may be an improvement over eyewitness testimony, though, which can still be rather unreliable.

Not only does fMRI help determine guilt and presence at crime scenes, but it also helps provide a better understanding of the human mind. For example, it can indicate the difference in brain patterns between psychopaths and those who, well, aren’t psychopaths, and the varying levels of brain development that people experience from youth into their adulthood, which are not only useful in a legal setting, but for our knowledge as a whole.

The ability to use fMRI for legal purposes and determining guilt will be the topic of discussion on a PBS documentary, “Brains on Trial with Alan Alda.” In it, Alda will moderate a panel discussing the issues related to using fMRI in a court of law and the techniques it’s used for.

While this technology is still developing, it’s doing so at a nice rate. It cannot yet completely prove one to be innocent or guilty, but it still has a decent success rate at the moment, and will continue to improve until it becomes completely reliable. As it does, we’ll see debate and discussion about the moral, legal, and ethical implications of scanning one’s brain, and if all goes well, it will help bring criminals to justice while letting the innocent walk free.