A Search Warrant For Your Brain?

In coming decades it may be possible to use brain imaging as legal evidence.

Carrie Peyton Dahlberg, Contributor

(Inside Science) -- Brain imaging can already pull bits of information from the minds of willing volunteers in laboratories. What happens when police or lawyers want to use it to pry a key fact from the mind of an unwilling person?

Will your brain be protected under the Fourth Amendment from unreasonable search and seizure?

Or will your brain have a Fifth Amendment right against self-incrimination?

“These are issues the United States Supreme Court is going to have to resolve,” said Nita Farahany, a professor of law and philosophy at Duke University in Durham, North Carolina, who specializes in bioethical issues.

Those legal choices are likely decades away, in part because the exacting, often finicky process of functional magnetic resonance imaging (fMRI) could be thwarted if a reluctant person so much as swallowed at the wrong time. Also, a brain exam couldn’t be admitted in court unless it worked well enough to meet the legal standards for scientific evidence.

Still, the progress being made in “brain decoding” is so intriguing that legal scholars and neuroscientists couldn’t resist speculating during a law and memory session earlier this month at the annual conference of the American Association for the Advancement of Science in San Jose, California.

Our brains are constantly sorting, storing and responding to stimuli. As researchers figure out exactly where and how the brain encodes information, the fMRI also becomes a tool that can decode that information. The fMRI can identify the portions of the brain that are active, based on the increased quantity of freshly oxygenated blood they draw. Already, brain decoding can perform a version of that old magician’s trick — guess what card someone is looking at — with better than 90 percent accuracy, University of California, Berkeley neuroscientist Jack Gallant told the group.

Farahany predicts that like most new science, brain decoding will break into the courtroom for the first time through a cooperative witness, someone who wants to use it to advance his or her case.

Stanford University law professor Henry Greely, who moderated the Feb. 13 law and memory session, suggested that a court might be especially open to novel techniques during the sentencing hearing in a death penalty case.

Both agreed that compelling someone to undergo a brain scan, the way a person might now be ordered to provide a urine sample or a DNA swab, would come much later. Even if the scan method were so non-invasive that some might argue it isn’t a search at all, Farahany thinks the courts will probably decide it is, and so will consider that you are protected from “unreasonable” brain searches. That, though, only means the authorities would need a search warrant for your brain.

As to self-incrimination, people cannot invoke the Fifth Amendment now to withhold certain purely physical information from their bodies, such as fingerprints. A court might draw parallels, she said, to brain activity.

Farahany has been monitoring early attempts to bring brain science into the courtroom with some sort of fMRI lie detection. So far, she said, no court has admitted it into evidence, concluding there is no scientific consensus that it works dependably.

Lie detection could prove much tougher than the more basic decoding going on in the lab, said Gallant, because lies are nuanced things, springing from a wide range of motives and emotional states.

Gallant is one of the best known researchers in a field that has been glibly described as computerized mind-reading. It is far from that, but brain decoding has made dramatic advances in visual imagery in Gallant’s lab. Some of his recent work has involved asking volunteers to watch a compilation of video clips showing brief glimpses of short scenes while an fMRI measures the oxygenation of blood in different parts of their brains. His lab’s computer models can then determine what that person might be watching when shown new video clips, ones that he or she has never seen before. This decoding can pick up general categories: woman, man, people talking, buildings or the ocean. But it won’t stop there.

“Brain decoding is going to keep getting better and better,” he said, because our understanding of how the brain encodes keeps growing. The two move in tandem, as inseparable as two sides of the same piece of toast.

We won’t need to wait for lie detector test results before brain decoding is capable of extracting information an investigator might want, such as the encryption code to a file or the combination to a safe.

“You could easily decode a number sequence from somebody’s brain from fMRI now. Internal, unpublished data from my lab suggests that would not be difficult to do,” Gallant said in a phone interview a few days after his talk.

What you couldn’t do, he said, is decode numbers from the brain of a squirming, uncooperative person who wants to mess with the MRI machine.

“No way,” Gallant said.

Not in our lifetimes. But in our children’s lifetimes? He’s pretty sure that improved techniques will emerge.

Carrie Peyton Dahlberg is a freelance writer based in Humboldt County, California. She tweets at @PeytonDahlberg.