Launceston Detective Inspector John King said a $50,000 reward for information leading to the conviction of Mr Barker's killer was still on the table.

Police have again appealed to an unidentified man seen talking to Mr Barker on the morning when he was murdered.

Mr Barker was shot and killed by an unknown assailant in his home on August 2, 2009.

No one has been charged with the 36-year-old's murder.

"The murder of Shane Barker remains an open case for Launceston CIB and we continue to receive and examine information we receive," he said.

"It's now approaching six years since Shane Barker was murdered in his home. We want to bring the offender to justice and bring some comfort to Mr Barker's family."

Detective Inspector King said CCTV footage existed of the unidentified man driving a white Toyota dual cab Hilux, with a white canopy and white Sunraysia mag wheels. It is a 1997-2005 model car.

The driver of that vehicle can be seen talking to Mr Barker outside his home on the morning he was murdered.

Footage of the conversation was captured about 10.30am the morning of Mr Barker's death.

Police still wish to speak to this man and he has not yet come forward to police.

"We need someone to come forward and tell us what they know about the murder, and after six years perhaps circumstances have changed enough for someone to open up," Detective Inspector King said.

"We encourage anyone who may have information about Mr Barker's death to contact us."

■ Police said the information can be given anonymously through Crime Stoppers on 1800 333 000.