Final answer:
The correct word to fill in the blank is 'expert' because experts bring additional perspectives and specialized knowledge that can help identify possible mistakes before a detailed analysis is conducted.
Step-by-step explanation:
The early appointment of an expert gives the Incident Commander (IC) another set of eyes, another viewpoint, and another consultant. Experts often have a good sense of the answer even before a detailed analysis, which serves as a method to identify possible mistakes and encourages a more thorough examination. Having an expert on the team can be instrumental in critical situations where specialized knowledge is required to make informed decisions and to scrutinize the steps taken during incident management.