Proving Fraud

Using the article below,explain who would likely have been called in as an expert witness in this case and why. Imagine the interview that took place with Jean Daniel Perkins. What would the interviewer(s) likely have taken into consideration during the interview?
https://archives.fbi.gov/archives/atlanta/press-releases/2011/atlanta-man-convicted-by-jury-for-multi-million-dollar-fraud-schemes