In 2000, several predominantly Muslim states in northern Nigeria formally adopted Islamic law as part of their legal system, despite concerns from the largely Christian population in the south and words of caution from Nigerian President Olusegun Obasanjo.

For followers of Islam, many edicts of morality and lifestyle are found in the body of Islamic law known as "Sharia" — a set of religious rules that are observed in various ways around the Islamic world.

The word Sharia means "the path to a watering hole." It offers guidelines for everyday life, including prayers and donations to the poor. As addressed in the Koran, Sharia prescribes modest dress for both men and women and has been interpreted to insist on single-sex schools and transportation.

Several factors determine the underpinnings of Islamic law. The Koran (the Islamic holy text), the Sunna (the prophet Mohammed's teachings) and Muslim scholars' legal rulings all contribute to the collective body of laws known as Sharia.

The laws contain violations known as "Hadd" offenses, which include sexual intercourse outside of marriage, alcohol consumption, highway robbery, theft and murder.

With the proper evidence, sexual offenses can carry a sentence of stoning to death or flogging. Theft can be punished by the loss of a hand.

Since Sharia is interpreted and practiced in different forms around the world according to each country's religious and legal leaders, not all predominantly Islamic societies implement such penalties for committing a Hadd offense.

Like several Middle Eastern countries, Egypt recognizes Sharia as part of its jurisprudence but chooses not to enforce severe Hadd penalties as part of state law. Instead, adultery is often punished with short prison sentences.

Parts of Sudan, Saudi Arabia, Pakistan and Iran are all known to have adopted the Sharia punishment code but still enforce its harshest penalties with varying levels of consistency.

Iran is one of the few countries known to have carried out death by stoning sentences. In other countries, these sentences are often commuted to lashings or prison terms.

By the time Muslim leaders in Nigeria adopted Sharia law as part of their state-run legal system, the precedent for using the system had already been set. In the area that would become northern Nigeria, the Islamic code had been practiced for centuries, until the region came under British rule in the early 1900s.

As a colonial power, the British allowed the use of Sharia in Nigeria, but did not permit the enforcement of amputations or executions as punishments.

After Nigeria gained independence from Britain, Nigerian leaders suppressed the use of Sharia penalties, fearing they would inflame tensions between Muslims in the north and Christians in the south — a tenuous relationship that has remained on a hair trigger for decades. For the most part, Nigerian military leaders relied on establishing secular courts that utilized British common law as a foundation.

Nigerian attorney Muzzammil Sani Hanga told the PBS program Frontline in 2001 that corruption and crime contributed strongly to the re-emergence of the Sharia penal code in certain states.

"Armed robbery was always increasing in this country, the disparity between the rich and poor is always there," he said. "I believe the clamor for the implementation of Sharia is like an open show of defiance against the government, which is perceived by the Muslims as the sole agent of corruption in this country."

Although Christians are not subject to Sharia law, its use in the predominantly Muslim northern states has created an atmosphere of unease and intimidation between religious groups, causing tensions that have often led to violence.

Nigerian leaders have also drawn a distinction between those who may use Sharia for political gains and those who want to observe the Islamic law solely for religious reasons.

"The genuine Sharia, Islamic Sharia, is part of the religion and is part of the way of life of a Muslim and part of the way of life of Nigerians. We have existed in that way from the time that Islamic religion arrived in our land," Obasanjo told the news service allAfrica.com in 2001.

"It is what I call political Sharia that is new and that will come and go, because if you want to use Sharia to achieve political ends it will not hold. It may stick for a while, but it will not hold," he said.

Sharia implementation continues to raise difficult questions in Nigeria and around the Muslim world on how to separate the secular and religious systems.

"Nigeria is the largest concentration of Muslims on the African continent," scholar on African studies Dr. Ali Mazrui told a conference sponsored by the Nigeria Muslim Forum in 2001. "The population of Nigeria, as we indicated, encompasses more Muslims than the population of any Arab country, including Egypt. But can the Sharia be implemented at the state level without compromising secularism at the federal level?"

Nigeria's Sharia law has recently gained attention because of Amina Lawal, a 30-year-old divorced Muslim woman who had a child out of wedlock. Evidence of adultery was considered strong enough that she faced charges in a Sharia court.

Lawal was convicted in March 2002, and a Sharia court sentenced her to death by stoning at Bakori in northern Nigeria's Katsina state. She appealed the sentence and is next scheduled to have her conviction reviewed on August 27. Lawal's appeal of the ruling is a complex process that could involve up to three courts, including Nigeria's Supreme Court.

Lawal's sentence and others like it have triggered outrage from human rights groups opposed to the death penalty and cruel physical punishments. For example, The Guardian newspaper reports that in 2001 a teenage single mother was given 100 lashes for adultery, despite her claims that three men gang-raped her.

In 2002, a man was sentenced to death by stoning for raping a 9-year-old girl. If carried out, the stoning would be the first death sentence completed since northern Nigeria re-implemented Sharia law.

-- By Maureen Hoch, Online NewsHour