An applicant for admission to the United States as a citizen of the United States has the burden of proving citizenship. Matter of GR, 3 I. & N. Dec. 141 (BIA 1948). Once the applicant establishes that s/he was once a citizen and the government asserts that s/he lost that status, then the government bears the burden of proving expatriation. Ibid. The standard of proof to establish expatriation is less than the clear and convincing evidence test as applied in denaturalization cases, but more than a mere preponderance of evidence. The proof must be strict and exact. Ibid.