Defense attorneys have always attempted to put their clients’ crimes in the context of the moment, from “crimes of passion” in the 19th century, to “temporary insanity” in the 20th. Neurobiological defenses based on brain injuries, psychological abuse and other “brain problems” have been rising sharply in the new millennium.

But what if the tables were turned? What if prosecutors started plunging into the brains of the accused, looking for little electrical flickers and other “clues” supplying proof of guilt?

A new analysis by a pair of professors says that current evidentiary standards will likely hold such evidence back from juries for the time being—but additional safeguards should probably be enacted to ensure no less than the “freedom of thought” in America.

“We conclude that while federal evidence rules constitute a substantial hurdle for the use of neuroscientific evidence, more ethical safeguards are needed to protect against future violations of fundamental rights,” they write.

The analysis, published recently in the journal Frontiers in Neuroscience, is authored by Calvin J. Kraft, of the Program of Liberal Studies at the University of Notre Dame, and James Giordano, of Pellegrino Center for Clinical Bioethics at Georgetown University Medical Center.

The use of neurobiological defenses has become “somewhat en vogue,” they conclude, based on analyses of the work of Nita Farahany, the Duke University legal scholar who is cited throughout the paper. (In previous interviews with Farahany, Forensic Magazine learned that the number of federal judicial opinions citing brain evidence grew at a momentous pace from 2005 to 2012. “Brain problem” defenses doubled between 2007 and 2012 alone, the Duke team reported in 2016.)

But brain scans are a burgeoning frontier, according to the new analysis. And it has yet to be seen how and when they will appear in American courtrooms.

Two current technologies purport to be able to perform a kind of “mind reading.” One is an EEG technique assessing P300 signatures, waves showing the brain is updating its “context”—and thereby providing an indication of deception (or lack thereof). Another is fMRI brain scans showing blood-oxygenation levels in the fronto-parietal lobes and networks of the limbic system, which claim deception detection accuracy rates of 90 percent or greater.

But the two academics then assess where these brain tests, both current and future, may run up against some of the fundamental protections in the Bill of Rights.

For instance, the First Amendment has been inextricably linked in a case law extending from speech freedoms to the ability to think that speech, as well, they write.

Fourth Amendment challenges about searches would also pose a challenge to brain scans, they add.

A suspect is also protected against self-incrimination under the Fifth Amendment, and is also afforded “due process” under the Fifth and Fourteenth alike, they argue.

One of the closest analogues currently is the polygraph, still tightly controlled when it comes to evidentiary value. For instance, the 1997 decision U.S. v. Scheffer excluded all polygraphs from federal courtrooms—and 29 states have followed suit explicitly. (The remaining states would only admit it before a judge and jury if both prosecution and defense consented.)

But what the technological future holds—and its scientific proof—remains to be seen.

“Yet, if (and arguably when) forensic neuroscience eventually meets the standards for admission of evidence, it is unclear if other rights will be so carefully safeguarded,” they write. “More than ever, the inviolability of the mind … appears to be a moral, rather than a natural, imperative.”

The two authors contend that current evidentiary standards are likely to continue into the foreseen future.

“For their part, the rules of evidence, especially at the federal level, will most probably continue to preserve due process to the extent that they have since the Daubert case,” they write, while still quick to include a cautionary note.

“For while Justice may be blind, she must remain vigilant, in order to insure that novel technology does not circumvent the mandates of law, and that law does not misconstrue the capabilities and/or limits of technology,” they conclude.