The key witness we never heard from in the Case Against Adnan Syed.

The Case Against Adnan Syed, was full of new discoveries and groundbreaking revelations about the case millions have been obsessed with since the award-winning Serial dropped in 2014.

The 1999 murder of Baltimore high school student Hae Min Lee and the conviction of her ex-boyfriend, Adnan Syed were well documented in the podcast, but HBO’s four part documentary has shown us that there is more to the story.

The behaviour of Don Clinedinst, the 22-year-old who Hae was dating at the time of her murder, was called into question, and there were revelations about what the prosecution’s star witness Jay Wilds has been up to in the last 10 years.

You can watch the series trailer here. Post continues after video. 

But there was another key witness in the case who didn’t get to hear from – Stephanie McPherson.

Fans of Serial will remember that Stephanie was one of Adnan’s best friends and was dating Jay at the time of Hae’s murder.

But while she made a statement to police at the time, she has never spoken publicly about what happened.

Adnan and Stephanie pictured together at the prom. Image: The Case Against Adnan Syed.

Speaking to the Express, Amy Berg, the director of The Case Against Adnan Syed, said she had tried to reach out to Stephanie for an interview.

She said: "The one person I really wanted to speak to from the beginning was Stephanie, but we haven’t spoken with her, unfortunately.

"Stephanie was Jay's girlfriend and Adnan and Stephanie had dated in middle school.

"The three of them spent much time together. They spent time together between January 15 and when Adnan got arrested so there are a lot of questions I have for her.

"I have written her letters, I have called her, I’ve had the door slammed in my face. It is just a real tragedy I didn’t get to speak to her because I always thought she would eventually come out and tell us what she knows."

In Adnan's version of events, on the day of Hae's murder he loaned his car and cell phone to Jay so he could go to the mall to buy Stephanie a birthday present.

He also said he was at a party with Jay and Stephanie when they first heard Hae was missing.

Stephanie also declined at interview with Sarah Koenig for Serial.

You can watch the four part series in full on SBS On Demand.

Read more:

Everything we learned from Hae Min Lee's diary entries in The Case Against Adnan Syed.

The tiny detail in Adnan Syed's phone records that won the convicted murderer a new trial.

The Case Against Adnan Syed achieved what Serial was never able to.