VA disability claims are not decided on the civil 'more likely than not' standard. Under 38 U.S.C. 5107(b), when the positive and negative evidence is in approximate balance, the benefit of the doubt goes to the claimant. Practically, that means an opinion at exactly 50 percent probability is enough.
How the standard maps to language
Raters read opinion language as a probability statement. Approximate mapping:
- 'Is due to' / 'is caused by' — near certainty
- 'At least as likely as not' — 50 percent or greater, sufficient to grant
- 'Less likely than not' — under 50 percent, supports denial
- 'Could be related' / 'is possible' — speculative, generally given no weight
- 'Cannot be determined without resort to mere speculation' — no probative value either way
Why rationale beats conclusion
Two opinions using identical concluding language can be weighted very differently. The Court of Appeals for Veterans Claims has repeatedly held that the probative value of a medical opinion depends on whether the examiner reviewed the record and gave a reasoned explanation. A conclusion without rationale can be dismissed. A thorough rationale is what survives review.