An pathologist claims a “single blow to the forehead” killed South Carolina teenager Stephen Smith, who had ties to the Murdaugh family.

Smith was found dead on a county road in July 2015 with a nearly 7½-inch fracture in his skull not far from the Murdaugh family estate.

The 19-year-old’s case was ruled a hit-and-run, before being reclassified as a homicide in 2021 after new evidence was brought forward by police investigating the shooting deaths of Maggie and Paul Murdaugh.

Forensic pathologist Michelle DuPre, who has performed more than 3,000 autopsies, speculates that a single blow to the forehead killed Smith, she told “48 Hours” in an exclusive clip obtained by The Post.

Because of the location and size of the fracture, she believes he was killed in the roadway, but denies the possibility that Smith was struck in a head-on.

While drawing on a foam head, she showed where the fracture would have been on his forehead.

“That’s 7½ inches almost,” she explains. The teenager also suffered another fracture to the back of his head when it hit the pavement, “splitting his skull,” according to the clip.

Smith was openly gay, and one of the many unfounded rumors which circulated since his death was that he was having a relationship with surviving Murdaugh son Buster. It had also been speculated that Buster and friends beat the nursing student to death with a baseball bat because he was gay.

Both of those rumors have been strongly denied by Buster.

He addressed the issue in the documentary “The Fall of the House of Murdaugh,” saying: “I never had anything to do with his murder and I never had anything to do with him on a physical level of any regard.”

DuPre also says the injuries don’t match Smith being beaten with a baseball bat.

“Those type of injuries would cause something that we call pattern injuries and we don’t see that here. This is a linear fracture,” she said.

Smith’s body did have a little road rash, but DuPre maintains that was “expected.”

She also dismissed that Smith’s body had been dumped there, as rumors had previously claimed.

Earlier this year, it was revealed that a rape kit had been ordered shortly after Smith’s murder, despite his death being classified as a hit-and-run, and an examination of his body for rape was reportedly ordered within 13 hours of the discovery of his remains, according to Mike Duncan, a now-retired corporal with the South Carolina Highway Patrol.

Smith’s mother, Sandy, has wanted a second opinion on her son’s death for years and says all she wants is the “peace in knowing what happened to my son.”

“He’s my world and I’ll fight ’til the end,” she told “48 Hours.”