This week, the Sixth Circuit affirmed a District Court's order denaturalizing a man who obtained his lawful permanent residence through a sham marriage. Notably, the immigrant failed to appear at the denaturalization hearing and presented no witnesses in his defense. The government presented the testimony of his ex-wife (with whom he entered into a sham marriage) and several of her friends, who testified that the couple never lived together, that the U.S.-citizen spouse continued dating other people, and that the couple planned to divorce before they married.
The full text of US v. Al-Sibai: http://www.ca6.uscourts.gov/opinions.pdf/15a0273n-06.pdf