Why Is Insider Trading Sometimes Civil and Sometimes Criminal?

Here’s  an easy-to-read primer by @WaltPavlo in @Forbes on the difference between civil and criminal prosecutions of insider trading: Insider Trading: Civil Or Criminal Crime?

In particular, note two observations: (1) the combination of new technology with old-fashioned mob and gang investigation tools (such as audio and video surveillance) means that developing evidence of wrongful intent is easier than in the past and (2) by anecdote, at least, civil defendants appear to be no more likely to re-offend than criminal defendants which, if supported by data, has implications for the proper exercise of prosecutorial discretion.