An inquest into the 55-year-old's death has been told she was checked on less frequently than was usual practice for drunk people in custody because of understaffing.

The grandmother fell and hit her head five times between 4.20pm and 6.40pm on December 5, 2017, after being arrested on a train at Castlemaine because she was drunk.

Someone as intoxicated as Ms Day should have been physically checked and roused every half-hour, a Melbourne inquest into her death was told on Wednesday.

But police decided to go up to her cell, but not inside it, every 40 minutes, and check her via CCTV every 20 minutes.

Watch house keeper Danny Wolters says this was because he didn't want to risk agitating Ms Day.

The Castlemaine Police Station also had some staffing issues.

Its Christmas party was that night but police from another station had been organised to fill in for some officers.

Leading Senior Constable Wolters saw Ms Day stumble drunkenly but "didn't actually see her fall over nor did I see her hit her head at any stage," he said in his statement to the inquest.

But this is not what the officer told emergency services when he called an ambulance that night after finding Ms Day with a raised bruise on her forehead.

In audio played to the Coroners Court, Const Wolters said he'd seen Ms Day slip about an hour beforehand.

Earlier that afternoon, Const Wolters stood outside the woman's cell for about five seconds to check on her seconds before she suffered her biggest and most catastrophic fall.

The officer said he didn't see this, and Ms Day replied "yes" when he asked if she was OK.

Later that night the woman was rushed to hospital and found to have bleeding on the brain. Seventeen days later, she was dead.

The inquest continues.

Australian Associated Press