Often they are committing new crimes, assaulting correction officers and other inmates.
It is the City Correction Department's dirty dark secret.
Up until now, Correction officers who are victims of violent inmates have often been afraid to speak out for fear of losing their jobs, inmates victimized by violent inmates are afraid for their lives, but the situation is so out of control that people are now coming forward.
On surveillance video, it shows the inside of Rikers Island.
The video shows a correction officer standing in the hallway while an inmate nearby sweeps the floor with a broom.
He eyed his prey and then started to swing viciously, striking the officer repeatedly on the head before other inmates jump into help.
The video is now evidence against inmate Robin Crosland, who is charged with assault.
He's a violent offender in jail for attempted murder, who should have been punished and segregated from staff and other inmates because of another previous jail assault, but he was not.
It's an all too common story.
"I pulled my hand back and all I saw was blood," said Rodney Brown, a correction officer.
Correction Officer Rodney Brown suffered a career ending attack by an inmate.
"He bit it off. One bite," Brown said.
It happened at the largest jail on Rikers Island as Officer Brown helped move inmates.
He had no idea that inmate Joseph Vilsaint, should have been in punitive lockdown for assaulting another correction officer a few weeks before.
His original charge was for assaulting two police officers in Brooklyn.
"He just leaped up swinging; hit me the head, the mouth," Brown said, "All I felt was a sharp pain on my hand, my right hand."
"And he had bitten your finger," Eyewitness News reporter Sarah Wallace said.
"Clean off. One bite," Brown said.
"What about the fact that he should have been locked down and wasn't and this never should have happened?" Wallace asked.
"Someone dropped the ball," Brown said.
The Correction Department acknowledges that an astounding 934 inmates should be in punitive segregation but are not.
They remain in general population.
It's called owing time in the box.
They're free to roam and often strike again.
Robin Crosland owed 107 days when he started swinging that broomstick.
"You come to jail and you continue to commit crimes and there's no discipline, no punishment, no nothing. You can do whatever it is you want to do when you're in the confines of the jail," said Norman Seabrook, President COBA.
Eyewitness News tried unsuccessfully for weeks to get an interview with the Correction Commissioner, and finally tracked her down last week at the Veterans Day parade.
"Where violence occurs we respond quickly with arrests, with separation of those inmates from other inmates," Correction Commissioner Dora Schirro said.
"But there are 900 inmates who should be in punitive segregation who are not, who are in general population; do you think that's appropriate?" Wallace asked.
"I think it's a real challenge for this agency and all other correctional systems around the country," Schirro said.
"But let me ask you, what message does it send to inmates who violate your own rules when they're not put in punitive segregation. What message does that send?" Wallace asked.
"Inmates who commit violent acts are placed in punitive segregation. The prioritization is individuals who assault staff, who assault inmates," Schirro said.
The Commissioner claims she's increased the number of punitive segregation beds but clearly, there aren't enough.
"It ended my career and I wasn't ready to stop working," Brown said, "What about other officers' safety? Someone could get killed."
If you have a tip about this or any other issue you'd like investigated, please give our tipline a call at 877-TIP-NEWS. You may also e-mail us at email@example.com.