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Electron paramagnetic resonance imaging (EPRI) also reveals the association between oxygen utilization and tissue-specific activation. It identifies paramagnetic species with unpaired electrons such as transitional metal complexes and ions. With recent availability of triarylmethyl-based radicals as endogenous tracers, EPRI's noninvasive imaging capability may be able to quantify metabolic processes at the cellular level.

At the Defense Academy for Credibility Assessment (DACA; Fort Jackson, Columbia, S.C.), formerly the Department of Defense Polygraph Institute, thermal imaging held significant interest as a tool for appraising trustworthiness. Specifically, DACA sought to quantify changes in facial blood-flow which often accompany induction of the sympathetic nervous system, when someone is anxious because (s)he is being deceptive. Initial findings were inconclusive; but, in 2000, Honeywell Laboratories (Minneapolis, Minn.) approached DACA with an improved infrared camera that returned accuracy rates in excess of 80 percent. Researchers continue to explore why blood tends to pool in the periorbital spaces and whether other facial areas can offer valuable insight.

DACA personnel also are examining laser Doppler vibrometry (LDV) for remote assessment of physiological reactions to stress. From a distance, LDV can pinpoint alterations in individuals' respiration, cardiovascular activity and muscle tone. The noninvasive technology may hold potential benefit for covert operation.

Brain Fingerprinting Laboratories, Inc. (Seattle, Wash.) pioneered testing to determine whether certain information is stored in a person's memory. Their approach assesses particular brain-wave responses to words, pictures and sounds. By recording reactions in fractions of a second after presenting a stimulus, the subject is unable to formulate or control a conscious reply. Three patents were issued to Chairman and Chief Scientist, Dr. Lawrence Farwell. And, in 2001, a State District Court (Pottawattamie County, Iowa) ruled that results of Brain Fingerprinting Laboratories' procedure were admissible in court for evidentiary purposes.

While at the Medical University of South Carolina (Charleston), Drs. Frank Kozel and Mark George demonstrated the power of fMRI to distinguish deception. In 2003, teaming with Dr. Steven Laken (Cephos Corp., Pepperell, Mass.), they filed patent applications disclosing their process. The polygraph measures peripheral effects of lying; hence, its relative unreliability. Since lying occurs in the brain, Cephos' method looks directly at the source.