38 C.F.R. § 3.304

(a) General. The basic considerations relating to service connection are stated in § 3.303. The criteria in this section apply only to disabilities which may have resulted from service in a period of war or service rendered on or after January 1, 1947.

(b) Presumption of soundness. The veteran will be considered to have been in sound condition when examined, accepted and enrolled for service, except as to defects, infirmities, or disorders noted at entrance into service, or where clear and unmistakable (obvious or manifest) evidence demonstrates that an injury or disease existed prior thereto and was not aggravated by such service. Only such conditions as are recorded in examination reports are to be considered as noted.

(1) History of preservice existence of conditions recorded at the time of examination does not constitute a notation of such conditions but will be considered together with all other material evidence in determinations as to inception. Determinations should not be based on medical judgment alone as distinguished from accepted medical principles, or on history alone without regard to clinical factors pertinent to the basic character, origin and development of such injury or disease. They should be based on thorough analysis of the evidentiary showing and careful correlation of all material facts, with due regard to accepted medical principles pertaining to the history, manifestations, clinical course, and character of the particular injury or disease or residuals thereof.

(2) History conforming to accepted medical principles should be given due consideration, in conjunction with basic clinical data, and be accorded probative value consistent with accepted medical and evidentiary principles in relation to value consistent with accepted medical evidence relating to incurrence, symptoms and course of the injury or disease, including official and other records made prior to, during or subsequent to service, together with all other lay and medical evidence concerning the inception, development and manifestations of the particular condition will be taken into full account.

(3) Signed statements of veterans relating to the origin, or incurrence of any disease or injury made in service if against his or her own interest is of no force and effect if other data do not establish the fact. Other evidence will be considered as though such statement were not of record.

(c) Development. The development of evidence in connection with claims for service connection will be accomplished when deemed necessary but it should not be undertaken when evidence present is sufficient for this determination. In initially rating disability of record at the time of discharge, the records of the service department, including the reports of examination at enlistment and the clinical records during service, will ordinarily suffice. Rating of combat injuries or other conditions which obviously had their inception in service may be accomplished pending receipt of copy of the examination at enlistment and all other service records.

(d) Combat. Satisfactory lay or other evidence that an injury or disease was incurred or aggravated in combat will be accepted as sufficient proof of service connection if the evidence is consistent with the circumstances, conditions or hardships of such service even though there is no official record of such incurrence or aggravation.

(e) Prisoners of war. Where disability compensation is claimed by a former prisoner of war, omission of history or findings from clinical records made upon repatriation is not determinative of service connection, particularly if evidence of comrades in support of the incurrence of the disability during confinement is available. Special attention will be given to any disability first reported after discharge, especially if poorly defined and not obviously of intercurrent origin. The circumstances attendant upon the individual veteran's confinement and the duration thereof will be associated with pertinent medical principles in determining whether disability manifested subsequent to service is etiologically related to the prisoner of war experience.

(f) Posttraumatic stress disorder. Service connection for posttraumatic stress disorder requires medical evidence diagnosing the condition in accordance with § 4.125(a) of this chapter; a link, established by medical evidence, between current symptoms and an in-service stressor; and credible supporting evidence that the claimed in-service stressor occurred. The following provisions apply to claims for service connection of posttraumatic stress disorder diagnosed during service or based on the specified type of claimed stressor:

(1) If the evidence establishes a diagnosis of posttraumatic stress disorder during service and the claimed stressor is related to that service, in the absence of clear and convincing evidence to the contrary, and provided that the claimed stressor is consistent with the circumstances, conditions, or hardships of the veteran's service, the veteran's lay testimony alone may establish the occurrence of the claimed in-service stressor.

(2) If the evidence establishes that the veteran engaged in combat with the enemy and the claimed stressor is related to that combat, in the absence of clear and convincing evidence to the contrary, and provided that the claimed stressor is consistent with the circumstances, conditions, or hardships of the veteran's service, the veteran's lay testimony alone may establish the occurrence of the claimed in-service stressor.

(3) If a stressor claimed by a veteran is related to the veteran's fear of hostile military or terrorist activity and a VA psychiatrist or psychologist, or a psychiatrist or psychologist with whom VA has contracted, confirms that the claimed stressor is adequate to support a diagnosis of posttraumatic stress disorder and that the veteran's symptoms are related to the claimed stressor, in the absence of clear and convincing evidence to the contrary, and provided the claimed stressor is consistent with the places, types, and circumstances of the veteran's service, the veteran's lay testimony alone may establish the occurrence of the claimed in-service stressor. For purposes of this paragraph, “fear of hostile military or terrorist activity” means that a veteran experienced, witnessed, or was confronted with an event or circumstance that involved actual or threatened death or serious injury, or a threat to the physical integrity of the veteran or others, such as from an actual or potential improvised explosive device; vehicle-imbedded explosive device; incoming artillery, rocket, or mortar fire; grenade; small arms fire, including suspected sniper fire; or attack upon friendly military aircraft, and the veteran's response to the event or circumstance involved a psychological or psycho-physiological state of fear, helplessness, or horror.

(4) If the evidence establishes that the veteran was a prisoner-of-war under the provisions of § 3.1(y) of this part and the claimed stressor is related to that prisoner-of-war experience, in the absence of clear and convincing evidence to the contrary, and provided that the claimed stressor is consistent with the circumstances, conditions, or hardships of the veteran's service, the veteran's lay testimony alone may establish the occurrence of the claimed in-service stressor.

(5) If a posttraumatic stress disorder claim is based on in-service personal assault, evidence from sources other than the veteran's service records may corroborate the veteran's account of the stressor incident. Examples of such evidence include, but are not limited to: records from law enforcement authorities, rape crisis centers, mental health counseling centers, hospitals, or physicians; pregnancy tests or tests for sexually transmitted diseases; and statements from family members, roommates, fellow service members, or clergy. Evidence of behavior changes following the claimed assault is one type of relevant evidence that may be found in these sources. Examples of behavior changes that may constitute credible evidence of the stressor include, but are not limited to: a request for a transfer to another military duty assignment; deterioration in work performance; substance abuse; episodes of depression, panic attacks, or anxiety without an identifiable cause; or unexplained economic or social behavior changes. VA will not deny a posttraumatic stress disorder claim that is based on in-service personal assault without first advising the claimant that evidence from sources other than the veteran's service records or evidence of behavior changes may constitute credible supporting evidence of the stressor and allowing him or her the opportunity to furnish this type of evidence or advise VA of potential sources of such evidence. VA may submit any evidence that it receives to an appropriate medical or mental health professional for an opinion as to whether it indicates that a personal assault occurred.