He was born in Brescia in a large family of Italian lawyers. His father, judge, will crown prosecutor in Palermo in the years following the unit.

     He was born in Brescia in a large family of Italian lawyers. His father, judge, will crown prosecutor in Palermo in the years following the unit.  After high school, he went to the criminologist Enrico Ferri studied law together with future members of the current Lombrosian: Guglielmo Ferrero or even Adolfo Zerboglio.  He spends his tesi di laurea the phenomenon of complicity.
     But it is two articles on criminal crowd, published in 1891 in the Journal of Cesare Lombroso, the Archivio di Psichiatria, he became known. These two items together form the core of his major work The delinquente Folla published shortly after and soon worldwide bestseller. The book quickly be translated into French under the title Criminal Crowd.
     The book discusses the phenomena of association, contagion and demonstrates the mechanisms involved in a crowd.
Sighele, it aims to demonstrate the criminal nature of collective associations (criminal crowd is composed of male criminals), however, highlights the psychological phenomena at work in moving away from the strict anthropological orthodoxy lombrosienne.
     Gustave Le Bon plagiarize his work (Gabriel Tarde called "a plagiarist doubled a photographer" in his correspondence). Sighele defends collective psychology left enough away from the lebonienne reading the crowd.
Sighele famous now expanding its research in the field of social psychology by focusing on the couple and the criminal sect.
     Zola, Durkheim and Nordau in France use his discoveries in various fields of literature, sociology or politics.
     Sighele published in France The psychology of cults (1895) and new editions of his magnum opus The Criminal Crowd where he forsake his increasingly negative reading from the crowd. He published a book in 1901 under prophetic "The intelligence of the crowd." At the time of the Dreyfus Affair, he was an ardent supporter of the innocence of the French officer in Italy.
     At the turn of the century, he became an activist in the Trentino , his home region, then under the domination of Austria . Sighele gradually abandoned the sociological work to indulge in journalism and political studies. His final work will focus on the national question and the irredentism that it is the theoretician.
     Expelled by the Austrians in the Trentino region because of its activism, he died in Florence in 1913.