The auditor must obtain reasonable assurance that the expert's work constitutes appropriate audit evidence in support of the financial information. He must therefore consider the source data used and whether it is appropriate in the circumstances, the assumptions and method used and their consistency with prior periods and the results of the expert's work in the light of the auditor's overall knowledge of the business and the results of his other audit procedures. He should satisfy himself that the substance of the expert's finding is properly reflected in the financial information. How appropriate, reasonable the assumptions and methods used are and how they have been applied is the expert's responsibility. The auditor does not have the same expertise so he cannot always challenge the expert's assumptions and methods. Although the auditor is not an expert on the expert's field of speciality, the auditor must be able to determine what is reasonable and what is not. Therefore he must obtain an understanding of the assumptions and the methods to determine that they are reasonable. There are times when the work of the expert does not support the related representations in the financial statements then the auditor should attempt to resolve the inconsistency by holding discussions with the client and the expert. He may need to engage another expert in resolving the inconsistency.
If after performing all these procedures the auditor concludes that:
i. The work of the expert is inconsistent with the information in the financial statement or that
ii. The work of the expert does not constitute sufficient appropriate audit evidence, then he should;
iii. Express a qualified opinion, a disclaimer of opinion or an adverse opinion as appropriate.