The policeman tasked with investigating Tanya Day’s death in custody said he did not question fellow officers about inconsistencies in their statement because asking follow-up questions was not “best practice”.

Det Sgt Scott Riley was the coronial investigator who produced the initial brief of evidence about the 55-year-old Yorta Yorta woman’s death for the coroner, Caitlin English.

Day died on 22 December, 2017, from a traumatic brain injury sustained when she fell in the Castlemaine police cells on 5 December. She was detained to “sober up” after being arrested for public drunkenness.

Riley told an inquest into Day’s death in Melbourne on Thursday that he chose not to ask police officers Edwina Neale and Danny Wolters about discrepancies between their statements and CCTV footage because he “considered it not to be best practice.”

“Best practice is to get a statement from the witness as soon as you can after the event,” Riley said. “That statement is their memory... in this case the statements are oversighted by [the professional standards command].”

Asked by the counsel for Day’s family, Peter Morrissey, if that would prevent him from asking a question if he was provided with inconsistent evidence, Riley said there was nothing to prevent him asking a question, “but it’s not the best practice”.

The officer from professional standards who had oversight of the investigation into Day’s death was Det Sgt Mark Patrick. He told the inquest that Riley’s view of best practice was incorrect.

“I believe that you should recanvass if required,” Patrick said.

Patrick said there were “no proposed policy or process changes recommended from the oversight process.”

He said that he concluded that Wolters had breached police guidelines by failing to conduct a welfare check every 30 minutes, and had been given “workplace guidance”. Neale was found not to be in breach.

Riley told the inquest that he had not attempted to locate any of the other passengers that were in the same V/Line carriage as Day.

He also had not attempted to obtain any CCTV footage of Day’s arrival at Bendigo hospital because he said he had not believed it to be relevant, and had not attempted to seize or even review CCTV footage of Day being wheeled out of the police station by paramedics.

“It’s probably an oversight,” he said. “Having said that, I don’t know that it would add a huge amount of value.”

He said he had not told doctors treating Day at St Vincent’s hospital the details of her fall, when he had identified it on CCTV, and had not considered doing so.

Under policies implemented following the royal commission into Aboriginal deaths in custody almost 30 years ago, deaths in custody are to be investigated as a homicide in the first instance before being determined a coronial matter.

Riley said he had investigated Day’s injury as a potential homicide and that the decision not to consider it a homicide was part of an “ongoing assessment” that could be reversed at any time, including as a result of new information arising from the inquest.

Asked whether he had any particular knowledge or training about the royal commission prior to Day’s death, Riley said, “I had knowledge of there being a royal commission but no training in relation to that and no knowledge in relation to it.”

“I believe I conducted a thorough investigation,” he said.

Emrys Nekvapil, a barrister for Day’s family, argued that since police replaced the process of charging and bailing a person for public drunkenness with issuing an infringement notice, there was no power to hold a drunk person in custody.

“It is simply beyond the power for police officers to do what they have given evidence in this case they did, which is to take someone into custody purely for their own safety,” Nekvapil said.

The inquest is expected to run until Friday.