What must an expert devote at least half of her professional time to?

An expert is expected to devote at least half of her professional time to active clinical practice or instruction because this level of engagement ensures that the expert remains current in their field and maintains a practical understanding of the subject matter. This requirement is particularly important in fields where expertise relies heavily on hands-on experience and ongoing education, such as medicine or psychology. Active clinical practice allows the expert to apply theoretical knowledge in real-world settings, which enhances their credibility when providing expert testimony or analysis. Instruction also plays a key role, as teaching others not only disseminates knowledge but also reinforces the expert's own understanding and mastery of the material. Engaging in active practice or instruction qualifies the individual as an expert, thus satisfying the legal criteria for being recognized as such in a court setting.