Tupac Shakur's murder suspect, Duane Keith 'Keffe D' Davis made a deal with federal investigators 14 years ago to speak openly about the rapper's killing.
Davis, known as 'Keffe D', is thought to have made a deal with federal investigators in California in 2009 that allowed him to speak openly on a number of topics - including what he knew about the hip-hop star's death in Las Vegas in 1996.
Experts are now warning that prosecutors may not be able to use the murder suspect's statements against him. If they attempted to, a legal dispute may break out in court, they warned.
The exact details of any agreement between Davis, 60, and federal investigators in 2009 are unknown, but officials may still be able to use his statements as an investigative tool as they continue to probe the case.
The self-described gangster made his first court appearance Wednesday, charged with Shakur's murder.
He was scheduled to be arraigned on the charge, but the hearing was cut short after he asked Clark County District Judge Tierra Jones to postpone the hearing while he retains counsel in Las Vegas.
Veronica Galván, a Washington state judge and a former lecturer at the National Judicial College in Nevada, told NBC that if an agreement was made 'there's some expectation that another jurisdiction would give full faith and credit to what this jurisdiction has done.’
'But I would also presume that that's done with the knowledge of that other jurisdiction, that it was communicated with that other jurisdiction, 'Hey, we're getting these statements, this is what we intend to do, are you cool with that?' And the feds normally do not make a proffer without bringing in the state' in the case of another crime being committed, the judge added.
Davis had been invited to speak to investigators over both the Shakur and the 1997 Biggie Smalls killings.
Tom Pitaro, a Las Vegas criminal defense lawyer, also told NBC that he was confident prosecutors would not use any protected words from Davis.
He said the prosecutors dealing with the very high-profile Shakur murder case would be very experienced and 'not rookies'.
Retired LA police robbery-homicide Detective Greg Kading said the deal may have prevented Davis's words from becoming self-incriminating, but officials could still use the information as an investigative tool.
He stressed the deal did not mean immunity even if there was an agreement that anything self-incriminating would not be used against him.
Kading added that once Davis left that room, the agreement was over.
'That agreement doesn't apply to everything else in his life, as he erroneously believed,' Kading said, 'so he began to go out and boast about his involvement in the murder.' The retired detective said this was not protected in the agreement.