Two Vancouver police officers fighting to halt an investigation into their alleged failure to warn a pregnant woman she was about to be killed, five days before she was stabbed to death in 2005, have had their petition dismissed by B.C. Supreme Court.

Investigations into the conduct of Det. Const. Craig Bentley and Staff Sgt. John Grywinski have dragged on without conclusion since they failed to notify 21-year-old Tasha Rosette when an informant told Bentley she was about to be killed.

Rosette was found stabbed to death outside the door of her Surrey apartment by her twin sister. She had been stabbed more than 40 times and her throat had been slashed.

Her boyfriend, Amjad Khan, who had been named by the informant, and Naim Mohammed Saghir, his alleged accomplice, were charged with her death in 2006 and a murder trial held in 2008.

Details of the tip Bentley received emerged during the trial, when the Crown alleged Khan wanted to kill Rosette because she was pregnant with his child and refused to have an abortion.

Khan testified in his own defence and denied having anything to do with Rosette's slaying or ever raising concerns about the pregnancy.

Khan and Saghir were found guilty but last year, the B.C. Court of Appeal overturned their convictions, ordering a new trial, which is set to begin in January.

Rosette's death also led to two complaints. The first was from her mother, saying Bentley and Grywinski should have warned Rosette she was in danger. The other came from Crown counsel and concerned police testimony at the preliminary inquiry of Khan and Saghir.

A Vancouver police investigation dismissed Rosette's complaint but did not consider the concerns of Crown, leading the Police Complaints Commissioner to order a new investigation.

In the hands of the Vancouver Police Department, the investigation continued for 18 months before the commissioner stepped in and ordered another inquiry be conducted by an outside agency.

Bentley and Grywinski went to court arguing the deadline for complaints had passed.

The B.C. Supreme Court heard Bentley told Grywinski, his supervisor, of the informant's tip off but the pair decided to further investigate the tip rather than warn Rosette.

In her ruling, B.C. Supreme Court Justice Laura Gerow said the police officers were using legal technicalities to avoid an investigation and dismissed their petition.

An external investigation into the officers' conduct can now proceed, seven years after Rosette's death.

With files from the CBC's Mike Clarke