 By 1547 , opposition to Calvin and other French refugee ministers had grown to constitute the majority of the <unk> , the civil magistrates of Geneva . On 27 June an unsigned threatening letter in Genevan dialect was found at the pulpit of St. Pierre Cathedral where Calvin preached . Suspecting a plot against both the church and the state , the council appointed a commission to investigate . Jacques Gruet , a Genevan member of Favre 's group , was arrested and incriminating evidence was found when his house was searched . Under torture , he confessed to several crimes including writing the letter left in the pulpit which threatened the church leaders . A civil court condemned Gruet to death and he was beheaded on 26 July . Calvin was not opposed to the civil court 's decision . 
