Over the past few years, with the reduction in the enforcement budgets of environmental agencies, there has been an increase in environmental tort litigation, and numerous geoscientists are being asked to testify regarding various related issues. Many are being asked to testify in areas for which they have little or no academic training and for which their opinions are based primarily on their experience and beliefs. This paper discusses how speculation and beliefs affect our predisposition to opinions and differentiates between opinions that are speculation and those that are well founded on fact and are legitimately based on sound scientific grounds. This paper discusses some of the different legal standards applied to testifying expert opinions. This paper also provides some examples of expert opinions from various case studies and discusses the ethical considerations of when it is or is not appropriate to offer opinions for which the primary basis is belief and not science.

Examples of plaintiff and defense Daubert challenges and recent court rulings are provided to examine whether ethics requires a higher standard than the guidance provided by recent rulings, given the limitations inherent in judges with poor technical backgrounds to serve as effective gatekeepers of misleading opinions. Examples of misleading opinions that are ethically and legally based on past precedents are summarized and discussed in order to provide a basis for a general ethical standard that attorneys and experts may find helpful in the future in deciding the scope of their opinions and what is required in terms of site-specific evidence for those opinions to be offered.

The ethics of typical opinions will be discussed for some of the areas about which experts may or may not be qualified to provide expert testimony. These areas include: ground-water supplies and the threats to such supplies, site investigation methods and procedures, their effectiveness and limitations, allocation of sources among contributing parties, natural attenuation, plume stability, uses and limitations of plume modeling, disclosure of confidential information and resulting jury contamination, among other topics.