His claim states the Crown has breached Treaty principles by failing to make a long-term commitment to reduce Maori re-offending.
Hemopo is seeking a recommendation that specific targets on Maori re-offending are set, and a long-term strategy developed in consultation with Maori.
Documents obtained through the Official Information Act showed Corrections had in 2013 let its Maori Strategic Plan lapse without any consultation with Maori, Hemopo told the tribunal.
A major problem was the transition between prison to probation. Hemopo said probation officers were "containment and compliance" officers, and were loaded with up to 80 cases at a time.
His lawyer, Peter Andrew, said the prison population would hit 10,000 next year, and about half of that muster would be Maori.
"Two-thirds of our youth in prison are Maori...the Maori statistics have never been so bad. That is the context to assess the Crown's Treaty obligations, and what we say are Crown breaches.
"In defending this claim the Crown points out the important issue of public safety and security. That, of course, is an important issue. But it is legitimate and essential to ask how secure and safe is our society long-term if these grossly disproportionately rates of incarceration continue."
Aaron Perkins QC, appearing on behalf of Corrections, cross examined Hemopo and pointed out a number of Maori-focussed initiatives had started since his retirement in 2011.
That included the creation of a director of Maori position, who heads a dedicated team of 24 staff, and is tasked with the development of a strategy to reduce Maori re-offending.
Corrections had "dozens and dozens" of regional-level initiatives partnering with Maori at a local level, Perkins said, and agreements in place including with Te Taumutu Runanga.
In addition, many Corrections-run rehabilitation programmes were tailored for Maori, including alcohol and drug rehab services. Marae-based services were also used, Perkins said, and case management officers assigned to prisoners were trained to recognise cultural differences.
Research was also being undertaken as to how to lower rates of Maori re-offending, and Maori were a cohort included in all pieces of research, he said.
"We are the most over-researched people in the world," Hemopo responded. "You can put fancy names to any programme. But the crux of my argument is that recidivism rates have not been reduced."
Asked for comment on Hemopo's allegations about some probation officers' attitudes to Maori, a Corrections spokeswoman told the Herald that comment could not be provided until the tribunal's decision had been made.
The tribunal hearing will close on Friday. It can make recommendations, but they are non-binding.
In 2004, the Waitangi Tribunal heard another urgent claim from Hemopo, alleging that an assessment system Corrections introduced to reduce reoffending had actually entrenched prejudice and discrimination.
Maori imprisonment
About 50 per cent of the male prison population are Maori, and almost 57 per cent of the female prison muster are Maori.
Maori make-up about 15 per cent of the general population.
Dr Jarrod Gilbert, a sociologist at the University of Canterbury, noted in a recent article that if Maori were imprisoned at the same rate as non-Maori, then the combined total prison population would reduce from 9400 to fewer than 4900.
