A true crime podcast has been credited with helping crack a decades-old cold case, leading to four men being charged over the killing of a teenage girl.

Roxanne Sharp, 16, was discovered dead in woodland in St Tammany Parish, roughly 50km north of New Orleans, on February 12, 1982.

The case proved difficult for detectives to solve, with little physical evidence and few witnesses prepared to speak up.

Investigators approached a local media company to produce the six-part podcast Who Killed Roxanne Sharp?

Louisiana State Police spokesperson Marc Gremillion said it was instrumental in gathering tips and encouraging new witnesses to come forward.

“It helped our investigators piece together where Roxanne was days before to the time she died to where we’re at now,” Gremillion told the Associated Press.

“It was a very large help with getting that message out to the public, and then, therefore, those witnesses getting back to us.”

The podcast that helped police charge four men four decades after the murder of Roxanne Sharp. Photo / Northshore Media Group

Four men have now been charged with aggravated rape and second-degree murder: Perry Wayne Taylor, Darrell Dean Spell, Carlos Cooper, and Billy Williams jnr, who are all in their 60s, the Associated Press reported.

Cooper and Taylor were already in prison for unrelated crimes, but Williams and Spell were arrested earlier this week, the outlet reported.

Sharp’s niece, Michele Lappin, issued a statement on behalf of the family, saying they appreciate the “hard work and love that has been shown to Roxanne Sharp’s case”.

“We hope that with justice will come healing and closure for our family, her loved ones, and the community.”

Vice-president of Northshore Media Charles Dowdy, who produced the podcast, was surprised by the level of interest.

“When we started the podcast, we kind of thought nobody cared - we were quickly corrected,” Dowdy said, Metro reported.

“A lot of people stepped up and said they knew Roxanne, they remembered her, they were friends with her.”

Dowdy spent time with police as they recreated the crime scene, recording audio and detailing the exact locations where Roxanne’s body and personal items were found.

“It clearly showed that she’d been grabbed on the street and dragged into the woods,” Dowdy said.

“Cold cases don’t close themselves,” Covington Police Department Chief Michael Ferrell said in a statement.

“They close because people show up, year after year, and refuse to quit. That is exactly what our agencies did, and, today, Roxanne and her family finally have the justice they have waited so long for.”