The family of a Fredericton woman who was poisoned to death in 2008 is calling for a coroner's inquest after police announced on Tuesday the case has been deemed "inactive" unless new information comes to light.

Patricia Ann Kucerovsky, a 43-year-old teacher and mother of two from the Beechwood Crescent area, died at the Dr. Everett Chalmers Hospital on Aug. 19, 2008.

Three years later, police ruled her death a homicide, saying she had died from mercury poisoning.

"I’d suspected from the beginning someone had done something to her because of how extreme her symptoms were," Lori Haggerty, the victim's sister, told CBC News.

Kucerovsky started slurring her speech, had severe pain throughout her body and eventually slipped into a coma, said Haggerty.

'This person still presents a danger to our community … And it would make us feel a sense of responsibility that we didn't stop this monster the first time.' —Lori Haggerty, victim's sister
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Patricia Ann Kucerovsky, a teacher and mother of two, died of mercury poisoning in 2008. ((CBC))

A 44-year-old male suspect was arrested in November 2011, but later released unconditionally.

On Tuesday, the Fredericton Police Force said investigators do not have sufficient evidence to lay a charge.

Haggerty fears the person who killed her sister will hurt someone else.

She said she believes a coroner's inquest would help provide some answers.

"There is the aspect that this person still presents a danger to our community and for us, as a family, if that were ever to happen, it would be like … reliving it," she said, fighting back tears.

"And it would make us feel a sense of responsibility that we didn't stop this monster the first time."

Const. Danielle Carmichael says police have exhausted every lead in the "very complex" and "highly unorthodox" case, but believe information is out there that would provide several missing pieces of the puzzle.

"There's no information to follow up on. So, it's not put on the back burner. It's not ranked any less of a priority. There's just no information coming in for us to actively investigate," said Carmichael.

"Should information come in, it would be reactivated immediately."

Kucerovsky had significant levels of mercury in her system. Police say it had been administered to her over several months.

Mercury poisoning damages the central nervous system and the kidneys, and in heavy exposure it can cause brain damage and ultimately death.