Distinguishing madmen and militants is never simple, but the Prosecution Project, led by Michael Loadenthal of the University of Cincinnati, analyses felony criminal cases involving political violence to see which ideologies are most common. The project examines criminal complaints, indictments and court records, looking for crimes that seek “a socio-political change or to communicate” to outside audiences, says Mr Loadenthal. Its data show that extremists on both left and right commit violence, although more incidents appear to come from right-leaning attackers (see chart 1). The figures do not, however, capture the severity of the crime nor the death toll. In 2001, for instance, there were more cases of right-wing violence than attacks by Islamists, even though the September 11th attacks by al-Qaeda killed almost 3,000 people that year.