Final answer:
The auditor's professional judgment is what ultimately determines the specific audit procedures necessary for an independent auditor to express an opinion, considering the company's environment and the effectiveness of its internal controls.
Step-by-step explanation:
The specific audit procedures necessary to provide an independent auditor with a reasonable basis for the expression of an opinion are primarily determined by the auditor's professional judgment. This judgment is informed by an understanding of the company's business and its environment, including the company's risk assessment, the auditor's risk assessment, and the effectiveness of the company's internal controls. While management's assessment of internal controls, the size of the company being audited, and the audit committee's approval may all influence the auditor's decisions, the auditor's own professional judgment ultimately dictates the nature, timing, and extent of the auditing procedures.
For example, in a situation where corporate governance fails, as with Lehman Brothers, where inaccurate financial information was provided to investors, the auditor would rely on their professional judgment to decide on additional procedures to respond to the perceived risks of material misstatement.