United States Court of Appeals
      for the Federal Circuit
                ______________________

              CHARLES L. KAYS, JR.,
                Claimant-Appellant

                          v.

  ROBERT D. SNYDER, ACTING SECRETARY OF
            VETERANS AFFAIRS,
              Respondent-Appellee
             ______________________

                      2016-1314
                ______________________

   Appeal from the United States Court of Appeals for
Veterans Claims in No. 14-1859, Judge Alan G. Lance Sr.
                ______________________

              Decided: January 25, 2017
               ______________________

   KENNETH M. CARPENTER, Law Offices of Carpenter
Chartered, Topeka, KS, argued for claimant-appellant.

    MARTIN M. TOMLINSON, Commercial Litigation
Branch, Civil Division, United States Department of
Justice, Washington, DC, argued for defendant-appellee.
Also represented by BENJAMIN C. MIZER, ROBERT E.
KIRSCHMAN, JR., SCOTT D. AUSTIN; Y. KEN LEE, MARTIE
ADELMAN, Office of General Counsel, Department of
Veterans Affairs, Washington, DC.
                 ______________________
2                                        KAYS   v. MCDONALD



    Before REYNA, TARANTO, and HUGHES, Circuit Judges.
HUGHES, Circuit Judge.
    Charles L. Kays appeals from a final judgment of the
United States Court of Appeals for Veterans Claims. The
Veterans Court affirmed a Board of Veterans’ Appeals
decision denying Mr. Kays’s claim for disability compen-
sation for post-traumatic stress disorder because he failed
to establish credible evidence of the in-service stressor
necessary to support a PTSD claim. On appeal, Mr. Kays
challenges the Veterans Court’s decision regarding the in-
service stressor and, particularly, the standard of review
it applied to the Board’s finding regarding the claimed
stressor. Because the Veterans Court applied the correct
standard of review, and because it correctly determined
that the regulations require credible supporting evidence
that the claimed in-service stressor occurred to the veter-
an, we affirm.
                             I
     Mr. Kays served in the United States Navy from Au-
gust 1972 to August 1976. In 2005, he filed a claim with
the Department of Veterans Affairs for benefits for disa-
bility caused by PTSD. He alleged that two non-combat
stressors during his service caused his PTSD. First, he
claims that he was stabbed during a fight as he left an
Enlisted Men’s Club. Second, he claims that while he was
off-duty and taking diving lessons, he was asked to help
with the recovery effort of a downed civilian helicopter.
When he dove into the water, he was separated from the
group and became stressed and scared.
    To establish that the alleged in-service stressors oc-
curred, Mr. Kays submitted statements, records, and in-
person testimony about the events surrounding the stab-
bing and the helicopter incident. Mr. Kays also submitted
a newspaper article entitled “Fatal ’Copter Crash Probed”
and dated Monday, January 12, 1976. J.A. 192. The
KAYS   v. MCDONALD                                         3



article describes how the Maryland state and marine
police investigated a helicopter crash that occurred the
preceding Friday. The pilot died three hours after the
accident and a helicopter mechanic was treated for expo-
sure and later released from a local hospital. The article
did not mention that any civilian diving students were
involved with rescue efforts.
     In 2005, the Regional Office denied Mr. Kays’s claim
for service connection for PTSD, and in 2007, the Board of
Veterans Appeals (Board) remanded for further develop-
ment of the record. The Regional Office again denied the
PTSD claim and, in 2010, the Board affirmed that deci-
sion. While this case was pending appeal at the Veterans
Court, the pertinent regulation, 38 C.F.R. § 3.304(f), was
amended and the Veterans Court issued a decision hold-
ing that the amendments to § 3.304(f) were retroactive.
See Ervin v. Shinseki, 24 Vet. App. 318 (2011). At the
parties’ request, the Veterans Court remanded this case
to the Board.
    The Board subsequently denied Mr. Kays’s claim for
compensation because he did not present credible evi-
dence establishing that the claimed stressors occurred.
Specifically, the Board found that statements by Mr. Kays
and his former spouse about the alleged stabbing were not
credible because they were unsupported and contradicted
by other evidence in the record. The Board also found
that Mr. Kays’s testimony about his involvement in a
traumatizing search and rescue was not credible because
of the lack of supporting detail in the article, his delay in
reporting the event, and his changing and inconsistent
story.
    Mr. Kays appealed to the Veterans Court, arguing
that it should review de novo the Board’s decision on
whether a veteran has submitted credible supporting
evidence that a claimed in-service stressor occurred. The
Veterans Court disagreed and found the Board’s decision
4                                        KAYS   v. MCDONALD



to be a question of fact reviewed under the clearly errone-
ous standard. Mr. Kays appeals. We have jurisdiction
pursuant to 38 U.S.C. §§ 7292(a), (c), (d)(1).
                            II
     We review questions of statutory and regulatory in-
terpretation de novo. Blubaugh v. McDonald, 773 F.3d
1310, 1312 (Fed. Cir. 2014). A non-combat veteran seek-
ing to establish service connection for PTSD must estab-
lish (1) a current medical diagnosis of PTSD; (2) a link
between the current symptoms and an in-service stressor;
and (3) “credible supporting evidence that the claimed in-
service stressor occurred.” 38 C.F.R. § 3.304(f). At issue
here is the third requirement—whether there is credible
supporting evidence that the claimed stressor actually
occurred. That is a factual determination, to be made in
the first instance by the Board, and reviewed by the
Veterans Court under a clearly erroneous standard. See,
e.g., Sizemore v. Principi, 18 Vet. App. 264, 270 (2004)
(“Whether a veteran has submitted sufficient corrobora-
tive evidence of his or her claimed in-service stressors is
also a factual determination that is reviewed under th[e]
[clearly erroneous] standard.”). Mr. Kays argues, howev-
er, that rather than a factual determination reviewed for
clear error, the credible supporting evidence requirement
is an “evidentiary burden” that should be reviewed de
novo by the Veterans Court. See, e.g., Appellant’s Br. 7;
Appellant’s Reply Br. 2–10. We disagree.
    As an initial matter, the language of the regulation
makes clear that the credible supporting evidence re-
quirement imposes a burden on the veteran to demon-
strate    that   the    claimed    stressor   occurred—a
quintessential factual inquiry. In similar cases, we have
rejected the argument that a veteran meets this burden
by pointing to any evidence. Instead, we have recognized
that when a statute or regulation requires a veteran to
demonstrate proof of an injury or event, the veteran must
KAYS   v. MCDONALD                                        5



put forth sufficient evidence to show that “it was at least
as likely as not that” the event or injury occurred. Holton
v. Shinseki, 557 F.3d 1362, 1370 (Fed. Cir. 2009). Fur-
ther, we have held that once such evidence is submitted,
it is incumbent on the Board to “evaluate the weight of
the evidence.” Id. That evaluation and subsequent
determination of whether an event occurred is precisely
the type of factual determination that the Board is tasked
with making. And that the Veterans Court reviews for
clear error. Sizemore, 18 Vet. App. at 270.
     Likewise, in Lennox v. Principi, 353 F.3d 941, 945
(Fed. Cir. 2003), we rejected a similar argument that the
Veterans Court should always review de novo a finding of
no service connection. We explained that de novo review
may be performed by the Veterans Court only when the
Board (1) has explicitly interpreted a statute or regulation
“concerning the correct standard for service connection,”
id., or (2) is “establishing a legal rule to be applied to
similar fact situations in future cases,” id. at 946. When
the Board is deciding disputed facts or applying estab-
lished law to the facts of a case, we held that those deci-
sions are “subject to review by the [Veterans Court] under
the clearly erroneous standard . . . .” Id. at 945.
    In this case, the Board did not explicitly interpret a
statute or regulation concerning the correct standard for
service connection or make a legal rule to apply in future
cases on the amount of evidence necessary for there to be
“credible supporting evidence.” Rather, it applied estab-
lished law to the specific facts of this case to find
Mr. Kays had not provided “credible supporting evidence.”
In other words, the Board made quintessential factual
determinations regarding Mr. Kays’s evidence, state-
ments, and credibility, and found that he was not entitled
to service connection. J.A. 164–75. The Veterans Court
appropriately reviewed these factual determinations
under the clearly erroneous standard.
6                                         KAYS   v. MCDONALD



    At oral argument, Mr. Kays appeared to raise a
slightly different argument relating to why the Veterans
Court’s decision affirming the Board should be reversed.
See, e.g., Oral Argument at 5:51–6:03, available at
http://oralarguments.cafc.uscourts.gov/default.aspx?fl=20
16-1314.mp3. According to Mr. Kays, § 3.304(f)’s re-
quirement to provide “credible supporting evidence that
the claimed in-service stressor occurred” requires only
evidence that the “stressor occurred,” not that it occurred
to the veteran. Mr. Kays argues that § 3.304(f)’s require-
ment that there be “a current medical diagnosis of PTSD”
ensures a nexus between the stressor and the veteran.
Thus, under Mr. Kays’s view of § 3.304(f), he needed to
provide evidence only that a helicopter crash occurred,
but did not need to provide any evidence that he got lost
participating in search and rescue activities.
     We find Mr. Kays’s interpretation of § 3.304(f) unper-
suasive. The regulation requires “credible supporting
evidence that the claimed in-service stressor occurred.”
38 C.F.R. § 3.304(f) (emphasis added). Here, Mr. Kays
claimed that his in-service stressor was getting lost while
participating in search and rescue activities after a civil-
ian helicopter crash. Accordingly, § 3.304(f) required
Mr. Kays to submit credible evidence that he was involved
in search and rescue activities and not simply that a
civilian helicopter crash occurred.
    Furthermore, Mr. Kays’s argument—that “a current
medical diagnosis of PTSD” assures that the in-service
stressor occurred to the veteran—misunderstands the
ordinary role of a physician diagnosing PTSD. A physi-
cian is not expected to do a detailed investigation of a
veteran’s claimed in-service stressors. And a physician’s
diagnosis of PTSD does not necessarily identify what
stressor caused it. Indeed, PTSD could result from an
event not identified by the veteran. That is why the
regulation requires the veteran to separately submit
KAYS   v. MCDONALD                                      7



credible supporting evidence that the claimed in-service
stressor occurred.
    Accordingly, because the Veterans Court applied the
proper standard of review, and because § 3.304(f) requires
credible supporting evidence that the claimed in-service
stressor occurred as claimed by the veteran, we affirm.
                      AFFIRMED
   No costs.