The FBI is consulting local police and vendors about technology currently in use that can spot crooks and terrorists by interpreting the symbolism of their tattoos, according to government documents.

The inquiry follows work already underway at the bureau and Homeland Security Department to add iris and facial recognition services to their respective fingerprint databases.

The FBI on Friday issued a request for information on existing databases "containing tattoo/symbol images, their possible meanings, gang affiliations, terrorist groups or other criminal organizations."

The mass collection of multiple biometric markers, potentially including vocal tracks and handwriting samples, has upset immigrant communities who say the FBI and DHS are misusing the technology to deport innocent people.

On July 11, the Wall Street Journal reported that the government denied green cards to spouses of permanent U.S. residents, some with no arrest records, because their tattoos resembled gang symbols. This week, a Senate panel is scheduled to question the FBI about the civil liberties consequences of facial recognition.

Friday's RFI asks law enforcement agencies, vendors and academics to supply by Aug. 13 information about the capabilities of tattoo analysis systems. The bureau is interested in learning how body art databases draw on the knowledge of gang experts and cryptanalysts as well as how they document "possible meanings and gang affiliations" observed by officials nationwide.

Privacy implications are only briefly addressed, in the context of policies regarding "what special guidelines will be followed when dealing with tattoos in 'sensitive' locations?"

The bureau also wants to learn about vetting pictures, sharing access to the database; and ways for multiple agencies to coordinate on data gathering.

The request does not discuss the reliability of such systems. Researchers at the University of Notre Dame recently found that iris patterns alter with age and the accuracy of sensors used to capture iris images degrades over time, raising doubts about the use of that single physical trait to confirm identities.

This article originally published at Nextgov here