“DID you kill Helen Munnings?”

It’s the question Australians will finally see asked to the last person to see the pregnant 20-year-old alive — her secret boyfriend Adam Taylor.

Ms Munnings was pregnant with her second child when she vanished from the Tasmanian town of Burnie on July 23, 2008.

Police say Mr Taylor, father of her then two-year-old son and unborn child, was the last person to see Ms Munnings before she mysteriously vanished.

She has not been seen or heard from since, with a 2012 inquest finding she “most likely” died that same day.

A promo for Channel 7 program Sunday Night shows Mr Taylor tracked down and asked the explosive question on camera.

He was a prime suspect in the investigation but has always denied any knowledge of what happened to Ms Munnings, with authorities unable to establish where her body might be or how she died.

The Channel 7 show also puts the police in the spotlight, questioning whether “crucial evidence” could have “gone missing” under their watch.

Ms Munnings' family were recently given fresh hope following announcement that the cold case had been upgraded to murder after police uncovered fresh leads.

Cold case unit Detective Inspector Rob Gunton said a “person of interest” had been identified and that a $100,000 reward remained in place for information leading to an arrest.

Mr Taylor began a sexual relationship with Ms Munnings while he was in a long-term relationship with another woman, Karalina Garwood.

He was 30 when he started sleeping with the 16-year-old.

Ms Munnings mother Karel Black attempted to have Mr Taylor charged with having sex with a minor, as the age of consent is 17 in Tasmania.

The couple secretly continued their relationship after Ms Munnings turned 17 and she gave birth to their son, Donovan.

It was not long before she disappeared that Ms Munnings told friends and family that she was pregnant again and Mr Taylor was the father.

Throughout the 2012 inquest it was heard that Mr Taylor was unhappy she was pregnant again and wanted her to get rid of the baby.

On the day of her disappearance she lied and told her mother she was walking to the doctor’s office, when in reality she was meeting up with Mr Taylor.

The two went for a drive together and Ms Munnings was never seen again.

Mr Taylor told the inquest the pair had driven around the greater Burnie area talking and he had dropped her off on the highway near the old pulp mill about 6pm before heading out on his boat.

On Monday it will be a decade since the pregnant mum vanished

Anyone with information about her disappearance is urged to contact Crime Stoppers on 1800 333 000.