What can potentially disqualify an expert witness from testifying?

An expert witness must possess relevant knowledge, skill, experience, or training related to the specific subject matter of the case in order to provide credible testimony. A lack of familiarity with the case details can hinder their ability to provide informed opinions or conclusions that assist the court in understanding the issues at hand. When an expert is not adequately familiar with the particulars of a case, their testimony may not be relevant or reliable, leading to a possible disqualification.

While controversial opinions may raise questions about credibility or bias, they do not inherently disqualify an expert from testifying. Similarly, having previous affiliations with one party could present a conflict of interest but does not automatically disqualify them unless it can be shown to affect their impartiality significantly. Certification from multiple organizations is typically seen as a strength, enhancing the expert's credibility rather than disqualifying them. Thus, the correct answer is based on the significance of familiarity with both the case details and the broader subject matter to fulfill the role of an expert witness successfully.