Stephen Smith -- the 19-year-old who was friends with Alex Murdaugh's son Buster and died 8 years ago -- was not killed in an accidental hit-and-run ... officials now say it was a homicide, and the change of heart has a link to the recent Murdaugh murder case.
The 19-year-old was found dead in the middle of a South Carolina road nearly 9 years ago. At the time authorities called it a fatal hit-and-run, despite glaring evidence it was foul play. Among the evidence -- there were no car parts found at the scene, and Stephen's body had no injuries below the torso.
The South Carolina Law Enforcement Division (SLED) announced they're reopening the case and investigating it as a homicide ... this based on new info they say they've gathered from the Murdaugh double murder case that just wrapped 2 weeks ago.
Unclear what exactly they've found or who it implicates ... but there's been widespread suspicion Alex Murdaugh's surviving son, Buster -- who was a former classmate of Smith's -- was possibly involved with him.
Buster addressed the speculation about him and Smith ... saying, "These baseless rumors of my involvement with Stephen and his death are false. I unequivocally deny any involvement in his death, and my heart goes out to the Smith family."
Smith's death case had actually been reopened in 2021, but SLED says they held off on announcing anything new until now due to the massive amount of attention on Alex Murdaugh's own murder case ... wanting to avoid ruining his chances at a fair trial. Now that he's been convicted, the word is out.
Smith's mother, Sandy, has been beating the drum about her son for quite a while now ... privately raising money to get his body exhumed/reexamined for a new autopsy.
An attorney for the Smith family came on "TMZ Live" Tuesday to lay out what he says is clear evidence that Stephen was murdered ... and that he still deserves justice today.