Final answer:
The Actus Reus in the assassination of Julius Caesar refers to the physical act of killing Caesar by the senators on the Ides of March in 44 BCE.
Step-by-step explanation:
In legal terms, Actus Reus refers to the physical act of a crime, which in the case of Julius Caesar's assassination, would be the actual stabbing and killing of Caesar by the senators. Considering the historical context, the senators, led by Brutus and Cassius, conspired and carried out the assassination of Julius Caesar on the Ides of March in 44 BCE. They performed the actus reus when they physically attacked Caesar, which resulted in his death. However, the legal system of ancient Rome differed significantly from modern law, and the concept of actus reus as it is understood today may not have been applied in the same way during that time.