South Australian police have been fined $390,000 over the death of a cook and cleaner who became trapped in a walk-in freezer at a police training centre in the Adelaide Hills.

But no officers or individuals will be held to account over the death of Debra Summers in 2016.

Summers died from hypothermia after becoming locked in the freezer at the Echunga facility.

Police pleaded guilty in the South Australian Employment Tribunal to breaching work safety laws and the deputy police commissioner, Linda Williams, said on Tuesday the force was “mortified” over the death of the 54-year-old.

“It’s terrible what happened to Deb. We are deeply sorry for the family,” she said. “We will never let anyone in our workplace down again.”

But Williams said a full inquiry had been conducted and no disciplinary action would be taken against any individual officers or staff over the incident.

The tribunal deputy president, Brian Gilchrist, said the death of Summers was both unexpected and preventable.

“No one deserves to die at work because of their employer’s lack of care,” Gilchrist said. “And there is no penalty that this court can impose that will right the wrong that has occurred.

“Nor can there be any correlation between the size of any fine that might be imposed and the value of Ms Summers’ life. Her life was priceless.”

In earlier submissions, the prosecutor Jeff Powell said issues with the freezer and problems at the training centre had either gone unnoticed or unattended to for years.

“Quite apart from the obvious and foreseen perils of someone working alone at a worksite, the precise issues with the walk-in freezer were not only foreseeable and obvious, they too were foreseen,” Powell said.

He said a technical document had detailed how the freezer should be serviced every six months, including a check of the emergency release system. Had the document been adhered to, “in all likelihood the precise consequences here would have been avoided”, the prosecutor said.

The SafeWork SA executive director, Martyn Campbell, said the fine imposed on police was one of the highest for a breach of work safety laws.

But Campbell said no financial penalty could make up for the loss the Summers family had suffered. “I hope that this judgement brings them a sense of justice and allows them to begin the healing process,” he said.