Hallucination Taxonomy

Definition: Direct quote does not appear in cited authority.

Evidence Requirements:

• Authority retrieved
• Exact quote not found in full text
• No near-match found (>85% similarity)

Example: Claim includes "quote text" attributed to judgment, but string does not appear.

4. PARAPHRASE_DISTORTION

Definition: Paraphrased content misrepresents authority's actual meaning.

Evidence Requirements:

• Authority retrieved
• Relevant section identified
• Content comparison shows material misrepresentation
• Not merely a summary or simplification

Example: Claim says "court held X" but judgment actually held "not X" or qualified differently.

5. AUTHORITY_NONEXISTENT

Definition: Cited authority cannot be found in public sources.

Evidence Requirements:

• Exhaustive resolution attempts (BAILII, legislation.gov.uk, nationalarchives)
• All candidate URLs attempted
• All return 404 or no relevant results
• Citation format appears valid (not obviously malformed)

Important: Only conclude this after retrieval attempts. Do not infer from citation pattern alone.

6. CITATION_MALFORMED

Definition: Citation string is structurally invalid or unparseable.

Evidence Requirements:

• Citation does not match any known citation format
• Cannot extract case name, year, court identifier
• Appears to be typo or garbled text

Example: "[202] UKSC" (missing digit), "Smith v [2023]" (missing opponent)

Classification Rules

1. Single category per claim-citation pair: Assign most specific applicable category

2. Priority order (check in this order):

   • CITATION_MALFORMED (structural issues first)
   • AUTHORITY_NONEXISTENT (retrieval failures)
   • PARAGRAPH_HALLUCINATION (specific locator errors)
   • QUOTATION_FABRICATION (exact quote errors)
   • PARAPHRASE_DISTORTION (semantic errors)
   • CITATION_MISMATCH (general content mismatch)

3. Evidence thresholds:

   • HIGH confidence: Direct evidence from retrieved source
   • MEDIUM confidence: Indirect evidence or partial retrieval
   • LOW confidence: Inference only, no retrieved source

4. UNVERIFIABLE_PUBLIC override: If cannot retrieve authority and not obviously malformed, use UNVERIFIABLE_PUBLIC instead of AUTHORITY_NONEXISTENT

Integration with public-source-gating

All hallucination classifications MUST respect public-source-gating tri-state outcomes:

• VERIFIED_ERROR → one of the 6 hallucination categories applies
• VERIFIED_CORRECT → no hallucination category
• UNVERIFIABLE_PUBLIC → cannot classify hallucination type

Output Format

For each claim-citation pair:

{
  "claim_id": "claim_1",
  "citation_id": "cit_1_1",
  "outcome": "VERIFIED_ERROR",
  "hallucination_category": "PARAGRAPH_HALLUCINATION",
  "confidence": "HIGH",
  "evidence_summary": "Judgment retrieved from BAILII; only contains paragraphs [1]-[35]; claim cites [42]",
  "evidence_details": {
    "retrieval_url": "https://www.bailii.org/...",
    "retrieval_timestamp": "2026-01-13T12:00:00Z",
    "cached_path": "sources/job_001/abc123...",
    "paragraph_count": 35,
    "cited_paragraph": 42
  }
}