Employee investigation can be conducted in response to a complaint filed against an employee during the course of their job, an allegation against a former employee, or an investigation about a new recruit. If you feel that a former employee created internal follies and has cheated the company in one way or the other, you can still investigate about the matter.
It is always better to go through the employee investigation process in early stages of a recruitment. Have a background check on your future employees, their previous work history, personal relations in the office (if any), assets owned, salary and criminal records with employee investigation.
The employee investigation process is conducted in a confidential manner so as to protect the identity of the employer. At the same time a prompt and effective investigation can help move the case forward.