The coroner presiding over the inquest into the death in police custody of Yorta Yorta woman Tanya Day has refused a request from Ms Day's family to remove an investigator from the case.

Key points: Ms Day's family sought to have a coronial investigator removed from the case over an email he sent to Victoria Police about the provision of evidence

Ms Day's family sought to have a coronial investigator removed from the case over an email he sent to Victoria Police about the provision of evidence The coroner regarded the investigator's email as more a case of "loose language" than an indication of flaws in the investigation

The coroner regarded the investigator's email as more a case of "loose language" than an indication of flaws in the investigation The inquest is scheduled to start on August 26

Ms Day, 55, died of traumatic brain injuries on December 22, 2017, after she was arrested for public drunkenness on a train at Castlemaine, in regional Victoria.

She sustained head injuries while in a cell at Castlemaine police station.

Acting State Coroner Caitlin English refused the request to remove her own coronial investigator, Detective Senior Constable Scott Riley, from the matter.

The family had made the request following the discovery that Senior Constable Riley had communicated with a division of Victoria Police about the provision of evidence which the coroner had ordered be provided.

The material concerned police procedures following a death in custody.

Senior Constable Riley wrote to the Victoria Police division that deals with the release of material, saying "I have spoken to my Senior Sergeant who believes this will probably go through. Can you please let me know what your thoughts are on this?"

Ms Day's family asked for the investigator to be removed from the case, saying the request suggested Victoria Police were filtering which evidence was released.

Tanya Day's children Warren, Apryl and Belinda, wanted the investigator removed from the inquest. ( ABC News: Jeremy Story Carter )

Barrister Sarala Fitzgerald told the court that Ms Day's family had long held concerns about the actual and perceived independence of the process, in which a police officer was responsible for conducting the investigation, given the actions of Victoria Police members were at the heart of the inquest.

"The investigation must be, and seen to be, conducted with the necessary levels of impartiality and independence," Ms Fitzgerald said.

Counsel assisting the coroner said the investigator's explanation for the email to Victoria Police was "to ensure he wasn't about to release anything that was the subject of public interest immunity".

Catherine Fitzgerald told the coroner she was satisfied Senior Constable Riley had acted independently and there was no glaring omission in the evidence ultimately provided.

The lawyer for Chief Commissioner Graham Ashton, Rachel Ellyard, said nothing had "been done behind the scenes".

She submitted that Senior Constable Riley's request was simply in accordance with police procedure.

Coroner English said the investigation into Ms Day's death was effectively completed, and she regarded Senior Constable Riley's email as being more a case of "loose language" than an indication the investigation may be fundamentally flawed.

She said she was not prepared to make the "dramatic decision" to remove him from the case.

She indicated his conduct in the investigation could be addressed during the inquest.

'We just want answers for our mum'

Ms Day's daughter, Belinda Stevens, told the ABC after the hearing that she was disappointed with the coroner's ruling.

"Police shouldn't be investigating police," Ms Stevens said.

"At the end of the day we just want answers for our mum and for people to be held accountable for their actions and the actions that people have failed to take.

"This is about truth."

The inquest is scheduled to start on August 26.