What are the common law restrictions to expert opinion evidence?

The common law restrictions to expert opinion evidence are primarily encapsulated in the assumption identification rule and the basis rule. These rules serve to ensure that expert evidence is reliable, relevant, and based on appropriate data or experience.

The assumption identification rule requires that experts must specify the assumptions they have made when forming their opinions. This is crucial because, without a clear understanding of these assumptions, the court cannot properly assess the validity of the expert's conclusions. It emphasizes that the foundation upon which an expert bases their opinion should be transparent and defendable.

The basis rule complements this by requiring that the expert's opinion must be rooted in a sound basis, such as scientific principles, established methodologies, or relevant experience. The court must be confident that the expert's reasoning process follows logical and accepted standards within their field. This ensures that opinions presented are not merely subjective but grounded in accepted practices and evidence.

These two rules together reinforce the gatekeeping function of the court concerning expert evidence, aiming to prevent unreliable or misleading information from influencing judicial outcomes. They establish a framework within which expert opinions can be evaluated and contribute to the integrity of the evidential process.

The other options, while they address aspects of expert evidence, do not capture the specific common law restrictions articulated through these