It is well settled that the Board "has the duty to assess the credibility and weight to be given to the evidence." Wood v. Derwinski, 1 Vet. App. 190, 193 (1991); Washington v. Nicholson, 19 Vet. App. 362, 369 (2005). The Board is certainly entitled to consider conflicting statements in weighing credibility. See Buchanan v. Nicholson, 451 F.3d 1331, 1337 (Fed. Cir. 2006) (Board can consider bias in lay evidence and conflicting statements of the veteran in weighing credibility); Caluza v. Brown, 7 Vet. App. 498, 511 (1995) ("The credibility of a witness can be impeached by a showing of interest, bias, inconsistent statements, or, to a certain extent, bad character."). As with any determination, however, the Board must explain the reasoning behind its credibility assessments. Its statement of reasons or bases must be adequate to enable an appellant to understand the precise basis for the Board's decision, and to facilitate informed review in this Court. 38 U.S.C. § 7104(d)(1); Allday v. Brown, 7 Vet. App. 517, 527 (1995); Gilbert v. Derwinski, 1 Vet. App. 52, 57 (1990).
The "lack of contemporaneous medical records may be a fact that the Board can consider and weigh against a veteran's lay evidence." Buchanan v. Nicholson, 451 F.3d 1331, 1336 (Fed. Cir. 2006). In other words, even in the absence of contemporaneous medical records, "the Board retains discretion to make credibility determinations and otherwise weigh the evidence submitted, including lay evidence." Jandreau v. Nicholson, 492 F.3d 1372, 1376 (Fed. Cir. 2007).
In Cartwright v. Derwinski, the Court found that a veteran having personal interest in the outcome may affect the credibility of the evidence but that the Board may not disregard a veteran's testimony simply because he or she stands to gain monetary benefits. 2 Vet. App. 24, 25 (1991). The Board is not permitted to find that lay testimony is necessarily not competent to establish a nexus. See Davidson v. Shinseki, 581 F.3d 1313, 1316 (Fed. Cir. 2009) (holding that lay statements may not be dismissed categorically on the ground that they are not competent evidence of nexus). The Board's assessment of the credibility and weight to be given to evidence is a finding of fact that the Court reviews under the "clearly erroneous" standard of review. 38 U.S.C. § 7261(a)(4); Wood, 1 Vet. App. at 193; Gilbert v. Derwinski, 1 Vet. App. 49, 52 (1990). "A factual finding 'is "clearly erroneous" when although there is evidence to support it, the reviewing court on the entire evidence is left with the definite and firm conviction that a mistake has been committed.'" Hersey v. Derwinski, 2 Vet. App. 91, 94 (1992) (quoting United States v. U.S. Gypsum Co., 333 U.S. 364, 395 (1948)).