The witness in the Keli Lane case who could have changed everything.

Keli Lane was 21 years old when in September, 1996, she went to hospital alone to deliver a baby girl. She hadn’t spoken to her family or friends about her pregnancy, and two days after giving birth, she attended a friend’s wedding with her boyfriend, Duncan Gillies. Not even he had known she was pregnant.

But that baby – Tegan Lee Lane – who would today be 22, has never been seen since.

Now, eight years on from being convicted of murdering her two-day-old daughter, Lane is determined to prove her innocence.

The 43-year-old reached out to award-winning Australian journalist Caro Meldrum-Hanna to investigate her story, which has now become the focus of new investigative ABC series EXPOSED: The Case of Keli Lane.

Watch the trailer for EXPOSED. Post continues after video.

In the second instalment of the three-part series, which aired on Tuesday night, Meldrum-Hanna and fellow journalist Elise Worthington started to consider the possibility that not all relevant witnesses had been interviewed by police.

A crucial part of Lane’s story is that she gave baby Tegan to her biological father, a man named Andrew Norris or Andrew Morris, who she had been having an affair with. She claimed she visited the man over the course of several months at his apartment in Balmain, but police said at the time they had found no evidence of the affair. Specifically, they claimed no one at the Balmain apartment block had ever seen Lane.

But Meldrum-Hanna and Worthington have identified a former resident who was never interviewed by police, who says he saw Lane at the property a number of times during the period she alleges to have been having an affair.

Darryl Henson lived in the Balmain apartment block up until the end of 1996, when Lane gave birth to baby Tegan. He is adamant that he saw Lane leaving through the car park several times while he was working on his car late at night.

When Meldrum-Hanna went to visit Henson in New Zealand, where he now lives, he positively identified the now 43-year-old from several photographs taken around the time of her relationship with Norris/Morris.

“I’ve got no reason to lie," he told the program. "I’d seen her coming and going through the carpark entrance, through High Street. I’m confident 100 per cent that I saw her.

“The jury should’ve heard everything. They should’ve heard from me too, just to clarify I did see her.”

“If Keli Lane had been seen in the vicinity of Wisbeach St, in or without the company of Andrew Norris, that immediately suggest that her story has an element of truth,” she said, describing the witness as "compelling evidence".

Tuesday's episode also revealed the very first forensic sketch of Andrew Norris or Andrew Morris, the man Lane says is the father of Tegan.

Good morning Twitter, for those who missed it, do you recognise this face? We are searching for the claimed father of Tegan and we’d like your help #EXPOSEDabc #KeliLane https://t.co/cDEw6to2GP @elisereports @JayaBalendra @JPursche @klipperdoc pic.twitter.com/z9L5NIBdMW

— Caro Meldrum-Hanna (@caromeldrum) October 2, 2018

When Lane was first approached by authorities in 1999, she gave several different accounts about what happened to Tegan, including denying she had ever had the baby. She is currently serving an 18 year sentence for murder and three counts of making a false statement on oath, and will be eligible for parole in 2023.