Explain in detail the high-level methodology used in digital forensic investigations. Explain the evidence collection process using this scenario and being mindful that there are live systems involved.

Digital Forensics Investigation

Imagine you are a digital forensics investigator hired by a corporation to secure and analyze a crime scene involving a misuse of company computer systems by an employee suspected of selling proprietary data to a foreign government over the course of several years.

Explain in detail the high-level methodology used in digital forensic investigations.
Explain the evidence collection process using this scenario and being mindful that there are live systems involved.
Discuss the importance of a secure chain of custody.