It has been four years since the mysterious death of a Fredericton woman, but police say somebody knows something.

The police made a plea for the public’s help with the cold case Thursday, as they continue to investigate the 2008 killing of Patricia Ann Kucerovsky.

"We are hoping that with the recent memorial held by Patricia's family and through our discussions today, that we can generate some new leads on the investigation," says Danielle Carmichael of the Fredericton Police Force.

Kucerovsky died in August 2008, but it wasn’t until last December that police ruled her death a homicide. They say she was poisoned with high grade mercury, which led to a slow and painful end.

Police believe there are people who know details of the case that they have not been able to uncover.

"We believe that there is someone who holds key pieces to this puzzle, someone who may have been in contact with Patricia and observed her deterioration or knows something that may be of help to police," says Carmichael.

Lori Haggerty is one of Kucerovsky’s six sisters. She says the lack of progress in the case is frustrating to the family.

"I believe they've done a very good job,” says Haggerty. “I know they've brought in outside resources and if the evidence was there for them to declare it a homicide, my question is, why hasn't the Crown decided to pursue this in the court system? Why haven't charges been laid?"

Police did arrest and question one unnamed male suspect. While he was released unconditionally, police say he remains their sole suspect.

Deborah Barter, another of Kucerovsky’s sisters, is hopeful someone will step forward after hearing the police plea.

"I certainly hope so. There has to be,” says Barter. “I really do believe that the missing pieces will be filled in.”

Police say the case will be solved, but only in conjunction with the community.

With files from CTV Atlantic's Andy Campbell