The rivalry and violence between Sunni and Shiite Muslims isn't just limited to Iraq. It is increasingly found in one place presumed shut off from the influence of faraway sectarian politics: New York's state prisons.

In the last two decades, the state's Muslim inmates, who number 7,987, have been increasingly identifying as either Sunni or Shiite, a phenomenon that prison chaplains elsewhere say is most pronounced in New York. Shiite inmates, who make up less than 4% of the Muslims incarcerated here, have long reported religious persecution by the Sunni-dominated Muslim chaplaincy employed by the state. The Sunni-Shiite divide has played a role in at least one stabbing between inmates in 2004, e-mails by prison officials show.

Shiite inmates have long demanded their own chaplains and a separate place to pray on Fridays, apart from other Muslim inmates. A little-noticed federal court ruling improves the prospects that Shiite inmates will see their demands met.

The recent ruling by the 2nd U.S. Circuit Court of Appeals opens the way for a trial in which jurors will weigh the demands of Shiite inmates seeking a separate Friday prayer service against the staffing and logistical concerns of prison officials. The court ruling overturns a court decision by a federal judge in Syracuse, Paul Magnuson, who ruled last year that Shiite Muslims could either pray individually from their cells or join the general Muslim service, which Shiite inmates say is Sunni-dominated. Noting that at least five Shiites are needed for a prayer quorum, Judge Magnuson said there even weren't likely enough participating Shiite inmates at any facility to constitute a valid communal prayer.

The 2nd Circuit's decision asks Judge Magnuson to look closer at whether joint prayer with Sunnis impinges on Shiite beliefs and at the prison system's capacity to accommodate separate prayer services. The three federal judges who sent the case back to Judge Magnuson were Roger Miner, Jose Cabranes, and Paul Crotty.

One chaplain said he was not aware of any other state prison system currently offering a separate Shiite service.

"I've not heard of that being a big issue in other places," a vice president of the American Correctional Chaplains Association, A.J. Sabree, said.

Imam Sabree, who is a Muslim chaplain in Georgia's state prisons, questioned why a prison system should distinguish between the two Muslim denominations when inmates from a variety of Protestant groups routinely pray together.

"That would be similar to Baptists saying they didn't want to worship with United Methodists," he said.

The New York State Department of Correctional Services offers a general Catholic and Protestant service, as well as occasional Greek Orthodox, Jehovah's Witness, and Seventh-day Adventist services, a prison spokesman, Erik Kriss, said. The state offers services for Jewish inmates, but does not distinguish between the various movements within Judaism. Services are also offered for inmates who follow Nation of Islam, Rastafarianism, and Native American religions.

But New York State has argued that a separate Shiite service in addition to the generic Muslim service would not be feasible because of space considerations and the funds required for staff to supervise another set of services. The official tally of Shiite inmates is 60, a prison spokesman, Erik Kriss, said, adding that the prison system estimated between 200 and 300 inmates identified as Shiite.

The prison system began counting Shiite inmates in 2001, although some refused to cooperate in the count. Doing so required filling out a "Change of Religious Designation Form," which, according to court papers, bothered some inmates, who said it was the prison's tallying system, not their religious beliefs, that had changed. In a given prison facility, there might be between three and seven Shiite inmates, according to several estimates.

The Friday prayer service of the two groups is generally similar in content. The most noticeable difference may be visual: Sunnis generally cross their arms during prayer, while Shiites leave them by their side.

One plaintiff, Antwon Dennis, who is serving a life sentence for murder, said in a deposition that he needs a separate service led by a Shiite inmate or chaplain for his prayers "to be valid."

The prison system's "failure to recognize that Shiite and Sunni Muslims have unique religious traditions, practices, and beliefs is incomprehensible," a lawyer for the plaintiffs, Claire Coleman of Brune & Richard LLP, said.

Depositions and an interview with one former inmate suggest that some Muslim inmates started identifying as Shiite while in prison beginning in the late 1980s. Several of the five Shiite plaintiffs were Sunni at one point. One plaintiff, Hussein Razi-Bey, 57, sentenced for attempted murder and kidnapping, found Shiite Islam after trying several other religions. During sentences in Minnesota and Missouri in the 1960s, Razi-Bey converted first to Nation of Islam, then to Catholicism, then to Baptism. Later, after several years with the Moorish Science Temple, he embraced Shiite Islam while incarcerated in New York, according to his deposition.

Inmates learn about Shiite Islam from other inmates and through mail order books received from publishing houses as far away as Iran, one former inmate, who asked not to be identified, said.

The plaintiffs say the more than 40 Muslim chaplains employed by the state are predominately Sunni and influenced by the Saudi Arabian movement of Wahhabism.

"In the places where it's been most tense, a lot of times the chaplains have been at fault," a Muslim chaplain who retired in 2006 from the prison system after 18 years, Dawoud Adeyola, said. He is not connected to the lawsuit.

The Muslim prison chaplaincy has been under scrutiny since a 2003 Wall Street Journal article disclosed that after the September 11, 2001 terrorist attacks, two New York chaplains spoke in support of the attacks.

The state prison system has reached out to Shiite leaders in the city for help in hiring Shiite chaplains for inmates, but those efforts have run into difficulties. An early candidate to be the prison's first Shiite chaplain was terminated during a try-out period after he was found trying to bring a knife into the Sing Sing Correctional Facility, one source said. The only Shiite prison imam, Muhammad Abdulmubdi, currently employed by the state is in an unusual position: He is barred from entering any prison pending the outcome of an internal investigation into whether he broke an undisclosed regulation, a source said. Mr. Kriss, the spokesman would not comment, and further details were not available.