Martinez-Galarza was detained by Immigration and Customs Enforcement (ICE) and pressured into giving them information about his nephew. ICE later used this information to deport his nephew. Martinez-Galarza applied for asylum, withholding of removal, and protection under the Convention Against Torture. His asylum and withholding of removal applications were based on his membership in the social group of consisting of "people who have provided information to ICE to enable that organization to remove individuals residing illegally in the United States" as well as a member of a second social group consisting of "witnesses for ICE."
The Eighth Circuit dismissed the appeal, finding that any harm that Martinez-Galarza's nephew would inflict on him would be because of a personal vendetta, and not because of his membership in the proposed social groups.
The full text of Martinez-Galarza v. Holder can be found here: http://media.ca8.uscourts.gov/opndir/15/04/141436P.pdf