of Muslim groups and populations exist, who favour the nationwide introduction of Sharia Law. The demands of these populations have been at least partially upheld by the Nigerian Federal Government in 12 states, firstly in Zamfara State in 1999. The implementation has been widely attributed as being due to the insistence of Zamfara State governor Ahmad Rufai Sani. The death sentences of Amina Lawal and Safiya Hussaini attracted international attention to what many saw as the harsh regime of these laws. These sentences were later overturned; the first execution was carried out in 2002. Blasphemy and apostasy Twelve out of Nigeria's thirty-six states have Sunni Islam as the dominant religion. In 1999, those states chose to have Sharia courts as well as Customary courts. A Sharia court may treat blasphemy as deserving of several punishments up to, and including, execution. In many predominantly Muslim states, conversion from Islam to another religion is illegal and often a capital offence. Demographic balance According to a Nigerian study on demographics and religion, Muslims make up 50.5% of the population. Muslims mainly live in the north of the country; the majority of Nigerian Muslims are Sunnis. Christians are the second-largest religious group and make up 48.2% of the population. They predominate in the central and southern parts of the country. For reasons of avoiding political controversy, questions of religion were forgone in the 2006 Nigerian census. History 2009 Boko Haram uprising Boko Haram conducted its operations more or less peacefully during the first seven years of its existence. That changed in 2009 when the Nigerian government launched an investigation into the group's activities following reports that its members were arming themselves. Prior to that the government reportedly repeatedly ignored warnings about the increasingly militant character of the organisation, including that of a military officer. When the government came into action, several members of the group were arrested in Bauchi, sparking deadly clashes with Nigerian security forces in Bauchi, Maiduguri in Borno State, Potiskum in Yobe State and Wudil in Kano State – which led to the deaths of an estimated 700 people. During the fighting with the security forces Boko Haram fighters reportedly "used fuel-laden motorcycles" and "bows with poison arrows" to attack a police station. The group's founder and then leader Mohammed Yusuf was also killed during this time while still in police custody. After Yusuf's killing, Abubakar Shekau became the leader and