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Tattoos are a complex form of art in modern society. First of all, they are expressive. People can incorporate certain words and symbols into a tattoo so that its design communicates something personal about their lives. In that sense, tattoos are also free speech, a legal right which is protected under the U.S. Constitution. The fact that people choose to obtain a tattoo by their free will further connote a deep relationship between body ink and freedom.

A tattoo’s multiple layers of meaning are not lost on government entities charged with upholding our freedoms. Some in the U.S. government are even working to develop technology that will help law enforcement use tattoos to profile criminals.

One of the most well-known of these initiatives is “Tattoo Recognition Technology.” Since 2014, NIST has been working with the FBI to develop tattoo recognition technology that will assist law enforcement agencies in their criminal investigations. A key sub-initiative was “Tattoo Recognition Technology Challenge” (Tatt-C), which was conducted back in 2015.

For that challenge, competitors were asked to develop tattoo recognition algorithms that could prove effective in one of five use-cases: tattoo similarity (matching tattoos across multiple subjects), tattoo identification (identifying a tattoo on one subject at multiple points in time), region of interest (focusing in on a smaller area contained within a larger image), mixed media (identifying similar images in different media formats, such as computer graphics, body art, pencil sketches, etc.), and tattoo detection (detecting whether an image contains a tattoo).

Using those algorithms, the U.S. government hopes it can eventually identify tattoos that “suggest affiliation to gangs, sub-cultures, religious or ritualistic beliefs, or political ideology,” as quoted on a Tatt slide created by NIST.

Tattoo Recognition Technology Raises Privacy, Legal Concerns(1)

Privacy advocates would argue that mindset leads to a slippery slope. From a legal standpoint, it’s unconstitutional for law enforcement to single individuals out based upon their religious beliefs, which in this case might take the form of people being seen with a cross or a Star of David tattooed on their arm. Freedom of religion is protected under the Bill of Rights, so the U.S. government can’t legally profile people based on their religious affiliations.

From a privacy standpoint, images don’t mean the same to one person as they do to another. If investigators spotted the same tattoo on multiple subjects, it doesn’t mean those people share a common affiliation. In fact, the design might hold a unique meaning for each individual.

Using tattoo recognition technology to suggest affiliations also disregards time. Even if the U.S. government were able to identify a subject walking around with a known gang sign tattooed on their body, the individual might not still be a member of that gang. They might have left years ago and might simply lack the funds, time, or commitment to get the tattoo removed.

The points explained above bring up some important free speech, privacy, and legal issues when it comes to tattoo recognition technology.

NIST's Official Tattoo Recognition Technology Logo
NIST’s Official Tattoo Recognition Technology Logo

Even so, the U.S. government’s implementation of Tatt-C caused an ethical challenge that might just outweigh all of those other concerns.

For the project, the U.S. government compiled a database of 15,000 tattoos. It did so by working with inmates in U.S. prisons who did not consent to the experiment, which violates government ethical research rules. Those kinds of experiments are supposed to be constrained by rules and overseen by an independent review board on which at least one prisoner sits as representative.

None of that allegedly happened in Tatt-C. According to a report published by the Electronic Frontier Foundation (EFF), researchers said the data was “operationally collected” on people who did not consent to participate, leading NIST to approve of the experiment retroactively.

“I don’t think researchers should be using prisoners as a free data resource,” EFF researcher Dave Maass told WIRED. “In this country, we have rules that are meant to protect prisoners, because of a long history of ethically challenged scientific research on them. If this study is going to use prisoner information, it needs to go through the highest possible scrutiny to make sure that people’s rights aren’t violated, and that prisoners know what has happened to them.”

In addition to highlighting the privacy and legal failures of Tatt-C, the EFF report highlights how NIST is planning to launch Tattoo Recognition Technology Evaluation (Tatt-E). That project “seeks to assess comparative and absolute accuracy, along with run-time measures on larger, operationally realistic datasets than seen in Tatt-C.”

For that initiative, the EFF says the U.S. government will need a larger number of tattoo images–as many as 100,000, in fact. If NIST decides to continue its work with the prisoner population, many more inmates could be deprived of their constitutional rights, argues the EFF.

With that being said, the privacy advocate group is urging NIST and the FBI to halt their activity until they’ve addressed the shortcomings of Tatt-C. As articulated by Maass and fellow researcher Aaron Mackey:

“Under federal research guidelines, research involving prisoners triggers enhanced scrutiny and ethical oversight to prevent their exploitation. Instead, NIST and the FBI are treating inmates as an endless supply of free data. Now, with NIST and the FBI on the precipice of a new, larger experiment that will use upwards of 100,000 tattoo images, officials must suspend any further research into tattoo recognition technology until they address the First Amendment, ethical, and privacy concerns EFF has identified.”

In the meantime, NIST has issued a response to EFF’s report, claiming that its project “has been reviewed and determined to not meet the criteria for human subjects research as defined by federal regulations. The NIST project is about measuring the effectiveness of algorithms for accurately matching digital images. The NIST project is not about the many complex law enforcement policies or approaches that may be related to images of tattoos.”

The institute has also since scrubbed references to religion and politics from its public documentation.

This is not the first time privacy advocates have smacked against the FBI in recent months. Last November, the privacy community expressed alarm at Tor’s allegations that the FBI paid researchers at the University of Carnegie Mellon that would help law enforcement unmask users of the anonymizing service. More recently, many activists also sided with Apple in the company’s decision to not assist the FBI unlock the iPhone of one of the San Bernardino shooters.