An investor is suing an auditor for issuing an unqualified opinion on the financial statements of Duluth Industries, which contained a material error. The auditor was negligent in performing the audit. The investor had reason to believe the statements were wrong prior to purchasing stock in the company. In the subsequent period, Duluth Industries sustained operating losses, the stock price went down by 40%, and the investor sold the stock at a loss. During the period that the investor held this stock, the Dow Jones Industrial Average declined 10%.

Required
What defenses might the auditor use?