Brain-imaging devices

DEFINITION: Instruments used to map regions of the brain or to measure brain responses to stimuli.

SIGNIFICANCE: Brain-imaging devices can be used to monitor brain activity to potentially determine whether a person is telling the truth and to perform postmortem mapping of the brain to determine whether death may have resulted from trauma to the head.

Brain-imaging devices are used to monitor brain activity. The patterns seen in brain imaging could potentially be indicative of whether a person is lying. The images are formed using magnetic resonance imaging (MRI). When experts examine the images to determine which areas of a person’s brain become active in response to questions, pictures, or other stimuli, this method is referred to as functional magnetic resonance imaging (fMRI). The subject is placed inside the scanning machine and allowed to interact with a computer screen to answer specific questions related to a crime. The MRI machine is interfaced with special computer software that captures specific brain patterns associated with lying, such as the blood-oxygen-level-dependent (BOLD) signals generated by specific locations in the brain. When a person is lying, these areas of the brain are more active than when the person is telling the truth. Hence, if the person is asked questions that will potentially elicit true and false responses, and if the blood flow is measured and mapped to the activity levels of specific brain locations during every response, then increased or changed levels could indicate instances where the person is lying. Even when a lie has been rehearsed in the mind of the subject, the captured images will detect a variation when the response is a lie. Despite promising applications, fMRI for lie detection is still being researched and is not considered a definitive or reliable method, as researchers have noted that the practical application of this method has many obstacles, including cost, subject participation, legal and ethical challenges, and real-world proof of its accuracy.

Although still undergoing development and refinement, the fMRI technique has many possible forensic applications. These include situations that involve libel, slander, fraud, or terrorist activities; the technology may also find application in the security screening of potential employees for important government positions. The technique might be used in the interrogation of criminal suspects or in the assessment of the intentions of prisoners before they are released. Because individuals involved in terrorist plots have detailed knowledge of plans and activities that innocent persons do not have, brain scans might be used to identify persons who have terrorist training and knowledge of terrorist activities.

The primary ethical issue that needs to be addressed in regard to the use of brain-imaging devices as lie detectors is that of the invasion of personal privacy. This problem may be resolved by safeguards that ensure that subjects are fully informed about brain imaging and agree to be examined in this way.

For examination of the brain after death, postmortem multislice computed tomography provides detailed in situ images of the brain. These are useful for screening corpses for foreign matter in the brain or for identifying whether head trauma resulting in skull fractures or cerebral hemorrhaging was the cause of death. Both two-dimensional cross-sectional images and postprocessed three-dimensional images of the skull can be made. Postmortem computed tomographic (PMCT) scans of an infant’s brain can reveal signs that are indicative of shaken baby syndrome (preferably called abusive head trauma). This type of child abuse is accompanied by subdural hemorrhage of ruptured cerebral bridging veins, which can be identified in PMCT images but is difficult to detect in a typical autopsy.

Bibliography

Brennen, Tim, and Svein Magnussen. “Lie Detection: What Works?” Current Directions in Psychological Science, vol. 32, no. 5, 2023, doi:10.1177/09637214231173095. Accessed 10 Feb. 2026.

Du, Bing, et al. “FMRI Brain Decoding and Its Applications in Brain–Computer Interface: A Survey.” Brain Sciences, vol. 12, no. 2, Feb. 2022, p. 228, doi:10.3390/brainsci12020228. Accessed 10 Feb. 2026.

Langleben, Daniel D., and Jane Campbell Moriarty. “Using Brain Imaging for Lie Detection: Where Science, Law, and Research Policy Collide.” Psychology, Public Policy, and Law, vol. 19, no. 2, 2013, pp. 222–34, doi:10.1037/a0028841. Accessed 10 Feb. 2026.

Quality Control Committee. “Uncovering the Truth with Functional Magnetic Resonance Imaging: The Future of Lie Detection.” British Polygraph Society, polygraph.org.uk/uncovering-the-truth-with-functional-magnetic-resonance-imaging-the-future-of-lie-detection/. Accessed 16 Feb. 2026.

Saferstein, Richard. Criminalistics: An Introduction to Forensic Science. 12th ed., Pearson Prentice Hall, 2017.

Tilstone, William J., et al. Forensic Science: An Encyclopedia of History, Methods, and Techniques. ABC-CLIO, 2006.

White, Peter, editor. Crime Scene to Court: The Essentials of Forensic Science. 4th ed., Royal Society of Chemistry, 2016.