David Joseph Hannan was 21 when he died. (Department of Justice)

Nova Scotia is offering a $150,000 reward for tips that help police solve a six-year-old crime in Dartmouth.

David Joseph Hannan was found unconscious near Harbourview School in December 2006. He died two days later.

Police believe Hannan was injured at the location where he was discovered. His death was declared a homicide.

The government is hoping that the cash reward will draw attention to the old case, and finally encourage people to come forward.

Halifax Police Chief Jean-Michel Blais said police believe someone has answers.

"With the passage of six years since his death, we hope the time may now be right for those people to come forward with crucial information that would help progress the police investigation," Blais said in a statement.