An inquest into the death of an inmate at the Otago Correctional Facility nearly four years ago begins in Dunedin today.

It's expected to take 10 days.

Jai Davis died suddenly in his remand cell two days after arriving at the Milton prison.

It's thought the 30-year-old died of a drug overdose.

He brought drugs with him when he arrived at the facility.

Nearly 60 people are set to give evidence over the two week hearing, they include Mr Davis' mother, corrections officials, police and medical experts.

Earlier this year police decided against laying any charges in relation to the death of Mr Davis.