When using testimony in a speech, which of the following characteristics of an expert is most important to establish with the audience?

Establishing competency is crucial when using testimony from an expert in a speech because it assures the audience that the individual has the necessary knowledge, skills, and credentials to speak on the subject matter. Competency reflects the expert's level of education, experience, and expertise in a given field, which helps build trust and credibility for the information being presented.

When audiences perceive that the expert has the relevant qualifications and background, they are more likely to accept and value the testimony provided. This is particularly important in persuasive speaking, where the speaker aims to influence the audience's opinions or actions based on solid evidence and credible sources. In contrast, characteristics like popularity, rationality, and success may not directly relate to the expert's actual ability to provide knowledgeable and reliable insight, making competency the most critical factor for the audience's trust and engagement.