In a precedential decision, the Ninth Circuit determined that an adverse credibility determination can be based solely on background documents. Though the Immigration Judge determined that the petitioner testified consistently, she also determined that the events about which he testified (namely, attacks and harassment by Sikh militants in 1998, 2005, and 2006) were implausible because the background documents indicated that Sikh militants stopped operating in the 1990s. The court acknowledged that its decision creates a circuit split with the Eleventh Circuit, which has held that an adverse credibility determination cannot solely be based on background documents.
The full text of Singh v. Lynch can be found here: http://cdn.ca9.uscourts.gov/datastore/opinions/2015/09/21/08-74212.pdf