Final answer:
Directly observable evidence is the most reliable type of audit evidence as it can be verified through the auditor's direct physical observation, making it less prone to manipulation.
Step-by-step explanation:
The most reliable type of audit evidence is directly observable evidence. This type of evidence refers to information that an auditor can verify through their own direct physical observation or inspection. Unlike evidence from within the client's organization or evidence from a poorly controlled system, directly observable evidence is less susceptible to manipulation or error. Facsimiles of documents, while useful in some circumstances, are not as reliable as the originals and thus are not considered the most reliable form of evidence. Therefore, an auditor seeking to gather the best proof to support their audit opinion will place a higher reliance on what they can directly observe.