Take a group of seven men and women inmates and follow their lives inside a corruption-ridden jail where violence is commonplace, a network of 300 cameras catching their every move and conversation.

So far, so normal for US television, but there is one important distinction: the "accused" are actually innocent volunteers planted in the jail -- and neither the other inmates nor the staff know that.  

Even by the standards of sometimes mind-boggling reality television in the United States, "60 Days In" is pushing the boundaries just a bit farther, earning rave reviews -- and a fair bit of concern too.

The 12-part "docu-series" -- which premiered last week on the A&E Network -- is centered on Clark County Jail in Jeffersonville, Indiana.

Its brainchild is county Sheriff Jamey Noel, who is determined to clear up a facility that even by the low standards of a jail is seething with graft and violence, and where drugs seem to be rampant.

"The only way to truly understand what was going on in the jail was to implement innocent participants into the system to provide first-hand unbiased intelligence," said Noel.

"The brave volunteers helped us identify critical issues within our system that undercover officers would not have been able to find."  

Among the volunteers planted among the 500 inmates in the jail, which heaves with everything from accused drug dealers to murderers, is the eldest of Muhammad Ali's nine children, Maryum.

A social worker in gang prevention, she had to change her name to prevent being recognized by the other inmates in the women's block.

- Threats, warnings -

The participants each have their own reason for putting their lives on hold for two months to experience what is a grim and highly volatile environment, leaving behind partners and small children.  

Several participants, including a teacher named Robert, believe jail is nothing more than a "country club" and wants inmates in the US to face tougher punishment.

Each is given a story that they are told to remember by heart so that when they are quizzed by the other inmates, they can convincingly rattle off what they supposedly did to land themselves in this hellhole.

The camera crew tell the other inmates and jail wardens they are there to film "first-timers" making their tentative initial steps into jail life. Only the seven moles and a handful of officials know the truth.

In a scene before the participants -- three of whom are women -- go into the jail, they are given alarming advice from a beefy official warning them how to behave inside: stay low-profile, but not too low-profile; tell the other inmates nothing personal; stick to the cover story; no drugs or violence.

The cocksure Robert instantly breaks every rule. On entering the jail block, he asks one man if they have the NFL channel on the communal television and his story of how he ended up behind bars quickly unravels when he keeps changing the details, revealing inconsistencies.

Placed in the most dangerous block in the jail, Robert's behavior makes for excruciating viewing and he raises the suspicions of his fellow jailbirds with everything from his attitude and haircut to the way he walks (the gait of a man used to carrying a gun on his waist, one inmate says, and word soon spreads that Robert is an undercover policeman).

Inmates huddle in darkened cells to speculate about their curious new jailmate, cameras catching them threatening to rape and beat him.

- 'Queasy feeling' -

Respected television pundits have widely lauded the program, while also voicing misgivings.

"For reality TV’s survival subgenre, the inside of a jail is one of the last frontiers, the claustrophobic flip side of stranding people on a remote island or in the Alaskan wilderness," wrote Brian Lowry, chief TV critic at industry magazine Variety, calling it "compelling."

However, Lowry questioned the judgment of Noel and the participants, and said that turning a jail into the backdrop for reality TV left a "queasy feeling."

He added: "Because while authorities might have benefited from this exercise, there’s a nagging sense that in terms of specific time frames, like most reality TV, '60 Days In' had more to do with 15 minutes of fame."

Kelly Khuri, a Clark County councilwoman, said that she only found out about the show from news reports and was quoted saying she did not think the jail's "deficiencies" should be aired on national television.

"I was very surprised. I'm very agitated and concerned because who ultimately is going to be responsible if there are any liabilities because of this high-risk venture?" she asked, according to Newsandtribune.com.