Jeff Manning of The Oregonian does a good write-up of a recent case against Flir in the federal court of judge Ancer Haggerty

The executives all hired Portland criminal defense lawyers, who soon believed that their clients' constitutional rights had been violated. Getting sworn testimony from criminal suspects under the cover of a civil investigation, violated their clients' Fifth Amendment rights against self-incrimination, they argued.

[ . . . ]

The law does not allow a prosecutor to make an "affirmative misstatement" or to lie about the existence of a criminal investigation. But prosecutors argued that the Flir defendants' lawyers never asked whether they were investigating. That prosecutors were interested shouldn't have surprised anyone, they argued in a brief to Haggerty, especially since many of the SEC interviews took place in the U.S. attorney's office.
[ Case's collapse reveals feds' tactics ]

The choice between civil action and criminal action is itself an interesting one. But here it gets more interesting because the civil action, and cooperation, was used to buttress a criminal action.

Off on a tangent:

Imagine being on the phone with the IRS and they say that "you must be hiding something" while they lie about your earnings. In a criminal action a lie would be official misconduct, and in a criminal case where the lie was the basis of a criminal judgment it would be a miscarriage of justice. However, it seems there are no such limits on government lying in a civil action, where bluster and demands for cooperation are repeatedly made. I refused to sign some stuff from the IRS because they kept whining for them needlessly, where their sole goal would be to subject me to perjury prosecution without regard to the truth or not. It became a matter of principal, their openly threatening desire to present false data to me and their apparent belief that the same false data could be used in a criminal case. Harassment and coercion based on misuse of one's official position can come in many forms.