Lucius Cassius Longinus was the brother of the Gaius Cassius Longinus, a leading instigator in the assassination of Julius Caesar.Around 52 BC, Lucius Longinus was triumvir monetalis in 63 BC. He minted denarii referring to the famous trial of the vestal virgins of 114–113 BC, which was prosecuted by his ancestor Lucius Cassius Longinus Ravilla. In 54 BC, he was the junior co-prosecutor to in the trial of for electoral malpractice .[1] Plancius was defenced by Cicero, who accused Longinus of incompetence, immorality and inexperience in his defence speech, the Latin: [[Pro Plancio]].[2]
Longinus was made a proconsul[3] by Caesar's appointment in 48 BC, during the civil war. He occupied Thessaly, but was forced by Metellus Scipio to retreat, after which he joined Calvisius Sabinus in Aetolia.[4] He was a tribune of the plebs in 44 BC, a year in which the people's tribunes were exceptionally numerous and his brother held the praetorship. Along with his fellow tribunes Tiberius Canutius and Decimus Carfulenus, L. Cassius was excluded from the important meeting of the Roman senate held November 28 to reassign several provinces for the following year.[5] A bill enabling Caesar to add new families to the patriciate[6] was probably sponsored by him rather than his brother as praetor.[7]