Labels would be reluctant to allow their artists to work with him, Ms. Oh added, “But they all think when he gets out of jail, he will be a big draw.”

[Read about 6ix9ine’s first, second and third days of testimony.]

Mr. Hernandez pleaded guilty in January to racketeering conspiracy and eight other charges. He faces a minimum of 47 years in prison. If his cooperation is successful, prosecutors agreed earlier this year to lobby for a lighter sentence.

His utility as an informant has an inevitable expiration date. Mr. Ellison’s and Mr. Mack’s trial is expected to conclude within days, and it is unclear whether Mr. Hernandez would testify in any other potential trials that could stem from the government’s case against Nine Trey.

Prosecutors have indicated he could enter the witness protection program.

Such a path would not be unprecedented. The government has successfully relocated and protected high-profile witnesses in the past; mobsters have started over as bakery owners, and reformed assassins have found new careers as doll salesmen, two former federal law enforcement officials said.

“Despite how connected we are, and the appetite for social media content in this country, there are places where, if this kid gets a haircut and wears normal clothes, no one would know or care who he is,” said Jay Kramer, a former F.B.I. official who worked on organized crime cases.

There is almost nothing in Mr. Hernandez’s background that suggests a capacity for discretion, and it is unlikely the United States Marshals Service, which runs the witness protection program, would pay for the removal of Mr. Hernandez’s signature face tattoos.

The rapper, whose rainbow-colored hair has faded to its natural black, transformed into a thoughtful, conscientious narrator in court. He paused frequently to translate street slang to the jury, and showed disarming flashes of naïveté — he asked lawyers to explain large words and requested clarification about questions.