The easiest explanation is a really short one - O.J. Simpson.
Translation: To very loosely paraphrase James Carville - Its the burden of proof, stupid.
Here's why the first real mortgage-backed-securities fraud case will be a civil action rather than a criminal prosecution:
In a civil action, a plaintiff (there is no prosecutor in the civil case) must meet the preponderance of the evidence standard in order to win. What is a preponderance of the evidence? 51%. The AG has, in other words, a pretty big margin of error.
In a criminal case, the burden of proof is the impossible to define, and very hard to meet, "beyond a reasonable doubt" standard. Or, as re-christened by the late, great Johnny Cochran, "if it does fit, you must acquit..."
To sum up: New York Attorney General Eric Schneiderman is no dummy. He wants to win.
By Brett Sherman
The Sherman Law Firm