A more thorough explanation:

Definition: Socius criminis refers to an accomplice or an associate in crime.

For example, if two people plan and execute a robbery together, they are both socii criminis or accomplices in the crime.

This term is often used in legal contexts to describe individuals who aid or abet in the commission of a crime.

The term can also be used more broadly to refer to anyone who is involved in criminal activity, whether or not they are directly participating in the crime itself.