Jaimie Byrne was supposed to be checked by nurses every 15 to 30 minutes while he was sleeping at Coffs Harbour Hospital in NSW on July 5, 2014.

But the 42-year-old was found dead inside the mental health unit the next morning, leaving his wife and seven children desperate for answers.

A joint investigation by Background Briefing and 7.30 has uncovered a series of critical failures by the Mid North Coast Local Health District.

It has also found staff on duty at the time were responsible for the care of another man who died at the facility under similar circumstances five years earlier.

Sarah Dingle investigates.