Expert opinion is not conclusive where documentary evidence supports local origin and no corroboration is produced.

Expert opinion under Section 45 of the Evidence Act is relevant but not conclusive, and it cannot by itself displace documentary material showing local manufacture and purchase. The Tribunal accepted challans, purchase particulars, and local producer records as reliable factual evidence, while the department relied mainly on expert opinion that some bundles were of Chinese origin and produced no further corroboration or verification of the documents. On that basis, the Tribunal's factual finding that the silk yarn was of Indian origin was upheld, and no substantial question of law arose for revisional interference.

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Issues: Whether the Tribunal's finding that the silk yarn was of Indian origin, based on purchase documents and local producer records, could be interfered with in revision when the department relied mainly on expert opinion under Section 45 of the Evidence Act.

Analysis: Expert opinion under Section 45 of the Indian Evidence Act, 1872 is relevant, but it is not conclusive proof and must be supported by other evidence. Here, the department relied only on the opinion of experts that some bundles were of Chinese origin, while the opposite party produced challans and purchase particulars showing local manufacture and purchase from producers. The department did not verify those documents or collect further supporting material. The Tribunal, as the final fact-finding authority, accepted the documentary evidence and rejected the department's case. No substantial question of law arose from that factual determination.

Conclusion: The Tribunal's factual finding was upheld and the revision was not entertained.

Ratio Decidendi: Expert opinion is only a relevant piece of evidence and cannot, by itself, displace a factual finding supported by documentary material when no supporting investigation or contrary proof is produced.

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