Expert opinion is a specialized conclusion or inference drawn by a professional in his or her area of expertise and used to help fact-finders understand complex issues in a case. As with any kind of evidence, there are several factors that determine the reliability of an expert’s opinion.
Regardless of the type of expert you hire, it is vital to provide them with all the background and information they need in order to reach their opinions. In particular, it is crucial to establish their qualifications and experience in the field and the scope of their expertise. This is important to ensure that they will be able to properly review and evaluate the evidence in a case, as well as articulate the opinions they are reaching to a jury.
An effective method of doing this is by preparing an outline for the experts before they begin their report. Providing the outline early on will help the experts focus on the most relevant areas for their report and avoid the temptation to stray outside of their specific scope of specialised knowledge in order to produce a ‘one stop shop’ kind of report. These types of reports can often be easily scuttled on cross-examination and will ultimately not be as persuasive as an early opinion that was built upon complete and accurate material.
It is also advisable to include in the letter of instruction any assumptions which the expert will need to rely on in producing their report. In preparing such a list, it is also helpful to highlight the reasons for the assumption to be made in order to prevent the potential for the expert to be accused of bias.