Intrusive Nature of Investigations
All investigations are intrusive. After all, who likes people rooting around in their affairs, whether personal or business? From the point of view of the potential witnesses, and civil libertarians, it makes for a lot of nervousness. All Americans, to greater or lesser degree, have sensitivity to their actual, or perceived, civil liberties.
Since the exact nature, extent and possible ramifications of the criminal activity being investigated are unknown or unclear-- people are disinclined to cooperate, or are at least nervous about it. After all, who wants to be a witness? People seem to have a sense that they will have some type of exposure because they are associated, even in an innocent way, with the fraudster and fraudulent activity. Many witnesses-- the “unconscious facilitators”-- have a sense they are victims, or assume they may have some liability. The unconscious facilitator is a person who unknowingly aids the fraudster in the commission of the crime. For example, the office assistant, who cut the checks to the phony business set up by the Accounts Payable Manager in order to form a “ghost vendor,” has no knowledge of the scheme, yet is very much a part of it (without culpability, most likely). He, or she, “facilitated” the scheme unconsciously. The assistant will be a key witness, not a co-conspirator but a facilitator, nonetheless. This is a tactical difficulty always is deeply rooted in the nature of fraud: deception, concealment, guile, taking unfair advantage of another.
From a shade-tree psychological aspect, the thoughts of betrayal and taken advantage of mill around in the witnesses’ mind. Moreover, being a witness is usually uncomfortable for most. (Why do you think prosecutors, and especially defense attorneys, call witness testimony in a trial the crucible of cross-examination? From the point of view of witnesses, “Who needs the aggravation?”