Expert opinion is a valuable tool when more rigorous survey techniques are too costly or when existing data are sparse (such as in population trend analyses). However, expert opinions can be highly susceptible to bias. For example, experts may weight their judgments based on the amount of uncertainty in an area, they could be biased by their personal views or beliefs, they might have a tendency to exclude certain views and information from consideration, or they might be prone to knowledge or experience bias.
In addition, an expert may use their opinion to influence the decision of others. It is important that lawyers are involved in the process of providing an expert with the necessary factual material and ensuring they are aware of all assumptions they are expected to adopt and are willing to consider alternate possibilities when appropriate. If instructing lawyers leave these matters unchecked, they risk end up with substandard expert reports replete with clunky factual logic and likely to be rejected by the Court if other factual findings are made.
When expert opinions are framed persuasively, they can strengthen an argument by adding credibility and weight to the claims made in an argument. This is particularly important for “experience goods” such as wine, where the customer is more likely to seek guidance from experts (Aqueveque 2006). Credentials of expert witnesses also play a role in an opinion’s effectiveness, with more impressive credentials, continuing education and experience in their fields tending to be more convincing.