diff --git a/packages/shared/src/research/claim-verifier.test.ts b/packages/shared/src/research/claim-verifier.test.ts
index 4598a13..896c3d9 100644
--- a/packages/shared/src/research/claim-verifier.test.ts
+++ b/packages/shared/src/research/claim-verifier.test.ts
@@ -41,6 +41,42 @@ describe('claim verifier', () => {
     expect(judge.calls).toHaveLength(0);
   });
 
+  it('fails closed without calling the judge when evidence content is blank', async () => {
+    const judge = judgeReturning('{"status":"supported","reason":"invented"}');
+    const result = await createClaimVerifier(judge).verify(
+      input('Revenue increased.', [{ id: 'e-1', content: '  \n\t' }]),
+    );
+
+    expect(result.status).toBe('insufficient_evidence');
+    expect(result.reason).toBe('invalid_evidence: evidence content must not be blank (index 0)');
+    expect(judge.calls).toHaveLength(0);
+  });
+
+  it('fails closed without calling the judge when an evidence ID is blank', async () => {
+    const judge = judgeReturning('{"status":"supported","reason":"invented"}');
+    const result = await createClaimVerifier(judge).verify(
+      input('Revenue increased.', [{ id: '  ', content: 'Revenue increased.' }]),
+    );
+
+    expect(result.status).toBe('insufficient_evidence');
+    expect(result.reason).toBe('invalid_evidence: evidence id must not be blank (index 0)');
+    expect(judge.calls).toHaveLength(0);
+  });
+
+  it('fails closed without calling the judge when valid and invalid evidence are mixed', async () => {
+    const judge = judgeReturning('{"status":"supported","reason":"invented"}');
+    const result = await createClaimVerifier(judge).verify(
+      input('Revenue increased.', [
+        { id: 'e-1', content: 'Revenue increased.' },
+        { id: 'e-2', content: '' },
+      ]),
+    );
+
+    expect(result.status).toBe('insufficient_evidence');
+    expect(result.reason).toBe('invalid_evidence: evidence content must not be blank (index 1)');
+    expect(judge.calls).toHaveLength(0);
+  });
+
   it('returns supported when the supplied evidence directly supports the claim', async () => {
     const judge = judgeReturning('{"status":"supported","reason":"The filing reports the same revenue increase."}');
     const result = await createClaimVerifier(judge).verify(
diff --git a/packages/shared/src/research/claim-verifier.ts b/packages/shared/src/research/claim-verifier.ts
index eb2afc7..331bff6 100644
--- a/packages/shared/src/research/claim-verifier.ts
+++ b/packages/shared/src/research/claim-verifier.ts
@@ -98,6 +98,18 @@ function result(
   };
 }
 
+function invalidEvidenceReason(input: ClaimVerificationInput): string | undefined {
+  for (const [index, item] of input.evidence.entries()) {
+    if (typeof item.id !== 'string' || item.id.trim() === '') {
+      return `invalid_evidence: evidence id must not be blank (index ${index})`;
+    }
+    if (typeof item.content !== 'string' || item.content.trim() === '') {
+      return `invalid_evidence: evidence content must not be blank (index ${index})`;
+    }
+  }
+  return undefined;
+}
+
 export function createClaimVerifier(client: JudgeClient): ClaimVerifier {
   return {
     async verify(input, signal) {
@@ -109,6 +121,11 @@ export function createClaimVerifier(client: JudgeClient): ClaimVerifier {
         );
       }
 
+      const invalidReason = invalidEvidenceReason(input);
+      if (invalidReason !== undefined) {
+        return result(input, 'insufficient_evidence', invalidReason);
+      }
+
       try {
         const reply = await client.complete(SYSTEM_PROMPT, userPrompt(input), signal);
         const parsed = parseJudgeResult(reply);