Henri Salvador Gutierrez had been in detention for seven months when an immigration judge ordered him released in June.

Gutierrez, a 19-year-old from Somerville, had been identified in a Boston police gang database as a member of MS-13, federal immigration officials had said, and should therefore continue to be held as the government worked to deport him.

But a federal immigrant judge ruled the gang intelligence was not reliable enough evidence to conclude the teenager was a member of the deadly international gang. Gutierrez was released and given permanent residency.

Less than six weeks later, on July 30, he and five other men allegedly stabbed 17-year-old Herson Rivas to death in Lynn.

Gutierrez later allegedly boasted that one of his alleged accomplices, Eliseo Vaquerano Canas, a.k.a. “Peligroso,’’ repeatedly stabbed the boy “as if he were a cow’’ while the teen begged for his life, according to court records. The boast was captured during a secretly recorded jailhouse conversation with a cooperating witness, according to federal filings in US District Court, while Gutierrez was in custody on an unrelated firearms charge.

The men allegedly belong to the Sykos Locos Salvatrucha clique of MS-13 and may have targeted Rivas because they believed he was cooperating with police, according to federal affidavits.

Rivas was stabbed dozens of times and left for dead in a wooded area near Henry Avenue Playground, prosecutors said.

“And Peligroso, dude, he was dicing him as if he were a cow, that [expletive]!’’ Gutierrez, who federal officials said goes by the nickname “Perverso’’ allegedly said in the jail conversation. “The knife Peligroso had, dude, looked like a saw now, dude. It broke, the son of a [expletive], on the cutting edge. It was warped. Because he was hitting him right on the skull, Clang! Clang! Clang! Clang!’’

Gutierrez’s arrest follows a heated debate about the Boston Regional Intelligence Center, which operates out of the Boston Police Department. The center, known as the BRIC, includes information about criminal activity and police observations of people associating with known gang members, information that can be shared with other local and federal agencies.

The American Civil Liberties Union of Massachusetts and other organizations have sued the Boston police in an attempt to force the department to release demographic information about who is included in the BRIC and how outside agencies access that data.

The lawsuit filed on Nov. 15 accuses Boston police of labeling Central American teenagers and young men as gang members or gang associates, often with little cause, and entering that information into a database that can be accessed by federal immigration authorities. Police have said the BRIC focuses on criminal targets and provides information that keeps the community and officers on the street safe.

The Globe wrote a story about Gutierrez’s case the day the lawsuit was filed. At the time, the Globe withheld his name at his lawyer’s request because he had received threats from a rival gang. Gutierrez’s case was not among the ones cited in the lawsuit as examples of men identified in the database.

Gutierrez was identified by the BRIC as a member of MS-13 based on several factors including his tattoo of the number “503’’ — the international telephone code of El Salvador — and his proclivity for wearing blue and white, colors favored by the gang.

The information had been collected by the BRIC and shared with the US Department of Homeland Security, according to a December 2017 report.

Investigators had “determined [him] to be a risk to public safety as a verified and active member of the MS-13 gang in the Boston metro area,’’ Homeland Security Investigations Special Agent Sean Connolly wrote in the report, which was used last summer in the teenager’s deportation proceedings.

But the immigration judge, Judge Mario J. Sturla, questioned the veracity of that evidence, citing, in part the testimony of Thomas Nolan, a retired Boston police lieutenant who has studied intelligence centers like Boston’s.

Nolan testified as an expert in the teenager’s case and said police failed to show he had committed crimes in connection with the gang, one of the requirements outlined in the federal guidelines for intelligence-gathering units.

On Saturday, Nolan said he stood by his testimony.

“His having a “503’’ tattoo, being in the company of another purported “verified’’ gang member when that individual was arrested, without any supporting documentation as to why that individual was “verified’’ as a gang member by the BRIC, ... are not indicative of reasonable suspicion of criminal activity,’’ Nolan said. “Particularly when there is no supporting information provided that would support such a contention.’’

In his June 22 decision, Sturla also cited Gutierrez’s cognitive disabilities, his testimony that he was abused in El Salvador, which he left to flee gang violence, and his stated desire to improve his life as factors in the decision.

“Lastly, the court finds that the respondent has made attempts to rehabilitate himself after multiple arrests for carrying knives and machetes,’’ Sturla wrote in his decision. “The respondent testified that he wants live a peaceful life.’’

Maria Cramer can be reached at mcramer@globe.com. Follow her on Twitter @globemcramer.