The Eleventh Circuit has determined than a petitioner who was held by fellow Contra rebels in a trailer was not confined to a prison, and therefore, did not commit a material misrepresentation in his adjustment of status application when he answered "no" to the question about whether he had ever been confined to a prison. The Court noted a prison is a state-run entity, and that confinement to prison implies legal authority to confine the person.
The full text if Alfaro v. Attorney General can be found here:
http://media.ca11.uscourts.gov/opinions/pub/files/201414913.pdf