Look for Horses, Not Zebras
It's based on the principle that horses are much more common than zebras (at least where I live), and therefore more likely.
It can also be applied to forensic accounting which uncovers fraud, or to any other crime.
While the crime may be complex, the fraudster's motivations are always simple: self-interest. That core need could be the money itself, a sense of entitlement, or a need to appear important and powerful.
In other words, rule out the obvious first.
There are many technological tools at our disposal to solve a crime, but focusing on the end result (in the criminal's eyes), can also uncover the fraudster, or at least narrow down the field. Technology and analysis provide the evidence to back it up.