On September 14, 1996, Keli Lane, smartly turned out in a cream Country Road pants suit, attended a friend’s wedding in Manly, Sydney.

A home video captures the water polo star casually taking her place in the pews holding hands with her then-boyfriend, Manly rugby union player Duncan Gillies.

Nobody, not even Gillies, knew that two days earlier, the then 21-year-old had given birth to a daughter.

Fourteen years later a court would find that in the four or five hours between being discharged from Auburn Hospital and dancing at the wedding, Lane murdered her newborn baby, Tegan Lee.

The surreal scene is just one of many staggering elements to the case which is now the subject of a three-part ABC documentary, Exposed: The case of Keli Lane.

The crime story made headlines from 2005 until 2011 when Lane was sentenced to 18 years in prison for infanticide.

Keli Lane is escorted by her father Bob Lane as they leave Westmead Coroners Court in 2006. Photo: AAP

The most intriguing elements of Lane’s legacy remain how she was able to conceal from those closest to her that by the time she was 24, she had given birth to three babies, in 1995, 1996 and 1999.

She gave up the first and third for adoption but the second, Tegan, vanished without a trace.

The web of lies take some untangling: Lane, the daughter of a policeman Rob and his wife Sandra, was a star athlete with hopes of making the Australian water polo team for the 2000 Olympics.

She first fell pregnant in 1992 at 17 to her high school boyfriend and decided with him to have a termination. A second abortion followed in 1994, both without her parents’ knowledge.

In 1995, she concealed a baby bump with jumpers around the waist before giving birth to her first baby girl hours after playing in the grand final of a suburban water polo competition.

She was 19 when she went into labour at a post-match function at the pub.

Keli Lane, left, at Taryn Woods 21st birthday party in 1996. Photo: AAP

She named Gillies as the father, without his knowledge. Teammates would later say they suspected her pregnancy, even sneaking a peek under the water with goggles, but said nothing because Lane acted like nothing was happening.

In 1999, after giving birth to her third baby, a boy, Lane, now working as a high school sports teacher, told a social worker during the adoption process that this was her first child and Gillies was the father, which he denied.

Suspicions were raised when her previous pregnancies were discovered, and DOCS worker John Borovnik reported baby Tegan as missing to the police.

Lane’s story changed multiple times since first being interviewed by police in 2001.

Initially, she said she had given Tegan to a Perth family. Later she claimed she had handed Tegan to her father (a man named Andrew Morris, who Lane said she had a brief affair with after meeting in a Sydney pub) on her way out of the hospital. In 2003, she said his name was actually Andrew Norris and after extensive searches, police concluded he was a fictional person.

A 2004 inquest lasted 18 months and in 2009, Lane, who by then had given birth to a fourth child— a daughter and was married to the girl’s father—was charged with murder and three counts of perjury.

In April 2011, she was sentenced to 18 years imprisonment with a non-parole period of 13 years and five months.

This September marks 22 years since Tegan’s disappearance and Lane, now 43, has spoken to ABC journalists Caro Meldrum-Hanna and Elise Worthington from inside Silverwater Women’s Correctional Centre for their documentary.

“The biggest hope for me is that someone comes forward with my daughter,” Lane says in Exposed.

“I don’t want to interrupt her life. I don’t necessarily even need to meet her. But obviously for my own family, for myself, I want to show that I did not harm her. And I certainly did not kill her.”

Exposed: The case of Keli Lane airs on the ABC on Tuesdays at 8.30pm from September 25.