The rapper known as "C-Murder," who once recorded an album while locked up in jail, may have done it again — this time in a maximum-security Louisiana prison, where he is serving a life sentence for a teenager's killing.

Prison officials are investigating whether the rapper, whose real name is Corey Miller, recorded music for an upcoming album while in the Louisiana State Penitentiary at Angola.

Miller, 45, is still challenging his 2009 murder conviction and life sentence. His latest appeal is pending before the Louisiana Supreme Court.

One of the songs on his latest album is called "Dear Supreme Court/Under Pressure" and includes a plea for the Supreme Court to free him.

"I had no gun. Didn't know the victim. My position still stands. It's blatant lynching of the system," Miller raps on a recently released video for the song. An actor portrays Miller in the video, which shows supporters holding "Free C. Miller" signs on the New Orleans court's front steps.

Miller denied recording anything at Angola but refused to take a polygraph test when investigators questioned him, state Department of Corrections spokeswoman Pam Laborde said in a statement.

In 2005, the rapper released an album recorded while he was incarcerated at the Jefferson Parish Correctional Center in Gretna. The recording, made with the help of an attorney, angered then-sheriff Harry Lee, who restricted what Miller's attorneys could bring into the jail.

Laborde said the current investigation began in January when reports of a new C-Murder album surfaced. It hasn't turned up any "conclusive" evidence that Miller recorded music at the prison, she said, but the investigation remains open.

The album "Penitentiary Chances" is scheduled to be released on April 15, according to Miller's manager, Manuel Ortiz.

Ortiz said Miller recorded all of the vocals on the album while under house arrest several years ago, before his 2009 conviction.

"He had a studio at his home," he said. "He has recorded an ungodly amount of unreleased music."

A judge sentenced Miller to life in prison in August 2009 after a jury convicted him of second-degree murder for the fatal shooting of 16-year-old Steve Thomas at a Harvey nightclub in 2002.

Rachel Conner, Miller's attorney, said her client is "justifiably frustrated" but hopes the Supreme Court "will give him his day in court."

"He is innocent of the shooting of Steve Thomas, and yet he is serving life without parole at Angola," Conner wrote in an email.

Laborde said prisoners aren't allowed to record albums or songs or maintain social media accounts. Accounts linked to Miller "appear to be very active," she added.

"The department regrets that the victim's family (and much of the public) cannot be spared from this," she said. "However, it appears that associates of the offender are responsible for content on these pages and it is very difficult for investigators to remove the pages."