Expert Witness’s Bias: Distinction Between Admissibility & Weight of Evidence


Generally, if there are concerns about an opposing party’s expert witness bias; it has been argued that their evidence has been given less weight. Recent decisions have been established that this measure is no longer effective, unless bias is sufficiently clear.  Although, bias can result in the disqualification of that expert, it cannot result in giving less weight to the expert witness’s admissible opinion.

Evaluating Evidence Under the Microscope

Admissibility & Weight of Evidence

In some cases, the Court has not agreed with the parties about admitting the evidence and then give it lessened weight because it is under its discretion to admit the evidence; even to decide that the expert witness is qualified or not to give testimony or opinion evidence.

Moreover, the Court has recognized that opinion evidence is inadmissible, unless the expert witness is qualified. By the same token, the Supreme Court has established that the elements of being qualified is; being independent, objective and impartial. Hence, a potential expert witness who is unable to carry through these duties to the Court is not qualified to perform the role of an expert witness.

The Court has also construed that bias and independence are strictly issues of admissibility, rather than weight; clarifying that there are other reasons why admissible expert witness evidence might be given less weight; for instance, if the evidence is not persuasive or helpful. Thus, the Court refuses to disqualify any expert witnesses based on the expert’s independence; even if, the expert’s independence has being attacked because it is not sufficient to warrant disqualification.

Bias Can Result in Disqualification of an Expert Witness

Bias Can Result in Disqualification of an Expert Witness

The outset for disqualification is great since pre-existing relationship with an expert witness does not automatically make the evidence of the expert witness inadmissible. Instead, there must be a reasonable concern that the expert’s testimony should not be admissible probably because the expert witnesses were unable to comply with their sworn duties.

In conclusion, attacks against experts’ bias and independence do not warrant their disqualification, unless the expert’s manifest bias is obvious. Consequently, impartiality is being relevant to both; admissibility and weight.



Related Articles:

Adversarial Bias: Expert Testimony In Modern Litigation

The Necessity of Properly Vetting Expert Witnesses

Expert Witness Methodology & Principles the “Key” to Admissibility