Jelly Roll has crossed the Thin Blue Line — the “Son of a Sinner” singer is now a Michigan cop.

“Never in his life did he think he would become a deputy!” a source exclusively tells Life & Style.

The recovering drug addict — who was arrested nearly 40 times during a misspent youth that put him behind bars on and off for about a decade — was sworn in at the Genesee County Jail after bankrolling a new recording studio at the facility to help rehabilitate inmates.

The Nashville heavyweight, whose real name is Jason DeFord, has credited music for helping him change his troubled life.

And when Sheriff Christopher Swanson pinned a bona fide badge on the 39-year-old “Save Me” singer, the lawman proclaimed, “Now that’s second chances!”

The insider says Jelly Roll was humbled by the honor — as he’s still recognized as a felon in his home state of Tennessee for a teenage robbery conviction.

“Jelly really believed at one point he was destined to spend the rest of his life in prison,” the friend says. “He’s turned his life around — and he’s trying to help other convicts do the same now.”