The usual allies disagree on the impact it will have on public safety.
The closure of Rikers Island was a big win for Darren Mack.
Not only did he advocate for it as part of Just Leadership USA, he was an inmate when he was 17.
"You either become a predator or prey," Mack said.
Mack served a 20 year sentence for being an accomplice to a robbery, including 19 months at Rikers.
"The dehumanization and brutality and violence that I have never experienced, to this day, never experienced in my entire life," Mack said.
Now, the city plans to build four much smaller, borough-based jails with more humane conditions by 2026.
The plan centers around the city's ability to drastically decrease the jail population from about 7,000 now to 3,300 inmates.
CBS2's Aundrea Cline-Thomas wanted to know if that was feasible, and what the impact could be to the community at large.
City leaders are banking on a continued decrease in crime. Add to that, nearly $400 million slated for rehabilitation, mental health and crime prevention initiatives.
In January, a new state law will eliminate cash bail for some misdemeanors and nonviolent felonies. That will cut the largest number of inmates - those incarcerated before their trial - by more than 60%, according to projections by the Department of Correction.
But O'Neill has concerns.
"That's going to put New Yorkers at risk. That's going to put victims at risk and it's going to put witnesses at risk," he said.
Former Manhattan prosecutor Lucy Yang now serves as the executive director for innovation in prosecution at John Jay College.
"We have to look carefully at each individual case and ensure that people who are truly a risk to public safety are not able to reoffend," she said. "But that can look like custody in some cases, or it can look like very intensive community supervision."
Today, little has changed for inmates at Rikers Island.
"The day when I will stand with the mayor and knock down the wall like the Berlin wall, when that day happens, I can be, like, done," Mack said.
He says this is just the first step, and more work to get to the root of the issue still needs to be done.
Crime is already at historic lows.
By 2026, the Department of Correction projects the jail population will mainly be made up of people charged with violent felonies.
for more features.