Duane "Keffe D" Davis -- the man recently convicted of orchestrating Tupac's 1996 murder -- is about to be sentenced ... and TMZ is streaming live.

The convicted killer is scheduled to appear in a Las Vegas courthouse Tuesday to learn his fate after he was found guilty in August on a murder charge.

As you know ... Keffe D was convicted of murder with the use of a deadly weapon with the intent to promote, further, or assist a criminal gang.

The maximum sentence he can receive is life in prison ... though he's made it clear to the judge he plans to appeal his conviction.

In a cover story published by The Hollywood Reporter shortly after he was convicted ... he insisted he was nowhere near where Tupac was killed.

He says he's totally innocent ... though he said in interviews for years he played a role in the rapper's death. His legal team says these claims were just the bragging of a man trying to profit off the horrific shooting.

Keffe D even claims he was at a bar in West Los Angeles near UCLA after the Mike Tyson fight ... far away from where Tupac was gunned down on the Las Vegas Strip.