DNA would normally be enough to catch a killer - but homicide detectives are hoping a $1 million sweetener will help solve the cold-case murder of a Melbourne sex worker.
Tracey Connelly, 40, was found dead by her partner in her Ford van in St Kilda just before 3pm on July 21, 2013.
She had upper body and facial injuries.
A DNA sample, which police believe belongs to the killer, was taken from Ms Connelly's van and police hope the reward will now lead to someone finally coming forward with information.
Despite numerous public appeals for information over the past six years, no one has been charged over her death.
About 1500 people gave a DNA sample to police during the investigation.
These included those who were in St Kilda at the time, had a history of violent offending and were registered sex offenders.
Detectives have also used the resources of law enforcement agencies interstate and overseas.
Homicide Detective Inspector Tim Day says police believe they can solve the case.
"It might have been almost six years since Tracey's death, however, I would like to strongly reinforce that this is both an active investigation and one that we believe is solvable," he said on Tuesday.
"This sample is going to remain in our system, while DNA technology only gets better and better with each passing month."
He urged anyone with information to come forward.
At the time of her death, Ms Connelly was estranged from her family and her partner at the time has since died.
A reward of up to $1 million will be paid at the discretion of the Chief Commissioner of Police for information leading to the apprehension and conviction of the person or persons responsible for the murder.
Police had initially thought Ms Connelly was killed during the day, but CCTV footage has since emerged of two people seen near the van on Greeves Street between 1.30am and 2.30am.
Detective Inspector John Potter said one of the people in the footage is believed to be Ms Connelly.
