Unlike lawyers, an auditor in an investigation is not guided by any rules of evidence and works alone without the competition of an opposing point of view. Any factual material available to an auditor which is pertinent to an evaluation of financial statements constitutes audit evidence and can be categorized as real, testimonial, or indirect evidence. Real evidence includes things actually examined by the auditor, while testimonial evidence is obtained through oral or written statements from other people. Indirect evidence encompasses documents, records, and events that the auditor uses in forming an opinion on financial statements. The reliability of audit evidence varies considerably among the major classes of evidence and within each class. Unwarranted inferences from audit evidence present a major danger, and the auditor should ascertain that any conclusions are based on specific evidential materials. The auditor must also be wary of misinterpretation, particularly with respect to evidence obtained from other people. Since relatively little audit evidence is fully conclusive, the auditor must be constantly concerned with the quality and quantity of the evidence and acquire more data if the available material is inadequate. In assessing the reliability of real evidence, the timing must be examined. Testimonial evidence poses additional problems of reliability based on the character and qualifications of the testifier. The auditor should consider the possibility of manipulation or falsification in indirect evidence, the atmosphere in which he is working, evaluate all available evidence, and from it infer the truthfulness of a financial statement.