Neighbours reported hearing a loud noise from the apartment between 9pm to 9.30pm.
Ms Howell was a singer who appeared on Countdown with 1970s top-40 hitmaker John St Peeters. No one has ever been charged over her death.
Police have now released a digital composite image of a man they wish to identify and speak to, following a review by homicide squad detectives this year.
Homicide squad lead officer Tim Day said investigators “strongly believe that this is a solvable case” once police are provided with the truth.
“Thirteen years is a long time for any family to wait for justice, but it might now be just the right time for someone to come forward with the answers that investigators need,” he said.
“History has shown time and time again that there will always be someone out there who knows the real story and I am urging that someone to come forward now and speak to us.
“Police have been told a lot of stories during the course of this investigation; now we’re waiting for someone to tell us the truth.
He urged anyone with information about Joanne’s death, including who is responsible and why, or anyone with information about the person shown in the image to please contact police.
“Police haven’t forgotten about Joanne and the community shouldn’t either – if you know anything, now is absolutely the time to come forward.”
It did not appear anything was missing or stolen from the unit.
Self-proclaimed pub karaoke king Paul Charlton, Ms Howell’s former partner, was arrested at the scene in April 2007 and later released pending further inquiries. He was 52 at the time.
A 2011 coronial inquest into the incident returned a finding that her former partner was likely involved in her death.
A Victoria Police spokesman said Ms Howell’s former partner remains a person of interest in the case.
The coroner also stated it was likely that an indictable offence had been committed in connection to Ms Howell’s demise.
Anyone with information that could assist investigators is urged to contact Crime Stoppers on 1800 333 000 or visit www.crimestoppersvic.com.au
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Ashleigh McMillan is a breaking news reporter at The Age. Got a story? Email me at email@example.com