The auditor shall design and perform audit procedures that are appropriate in the circumstances for the purpose of obtaining sufficient appropriate audit evidence.  (Ref: Para. A5‑A29)

When designing and performing audit procedures, the auditor shall consider the relevance and reliability of the information to be used as audit evidence, including information obtained from an external information source.  (Ref: Para. A30‑A44)

If information to be used as audit evidence has been prepared using the work of a management’s expert, the auditor shall, to the extent necessary, having regard to the significance of that expert’s work for the auditor’s purposes:  (Ref: Para. A45‑A47) 

1. Evaluate the competence, capabilities and objectivity of that expert;  (Ref: Para. A48‑A54) 
2. Obtain an understanding of the work of that expert; and  (Ref: Para. A55‑A58) 
3. Evaluate the appropriateness of that expert’s work as audit evidence for the relevant assertion. (Ref: Para. A59)

When using information produced by the entity, the auditor shall evaluate whether the information is sufficiently reliable for the auditor’s purposes, including as necessary in the circumstances: 

1. Obtaining audit evidence about the accuracy and completeness of the information; and (Ref: Para. A60‑A61) 
2. Evaluating whether the information is sufficiently precise and detailed for the auditor’s purposes. (Ref: Para. A62)

When designing tests of controls and tests of details, the auditor shall determine means of selecting items for testing that are effective in meeting the purpose of the audit procedure.  (Ref: Para. A63‑A67)

If: 

1. audit evidence obtained from one source is inconsistent with that obtained from another; or 
2. the auditor has doubts over the reliability of information to be used as audit evidence, 

the auditor shall determine what modifications or additions to audit procedures are necessary to resolve the matter, and shall consider the effect of the matter, if any, on other aspects of the audit.  (Ref: Para. A68)