The role of a therapist is to develop an evidenced-based personalized treatment plan for a client and to support and motivate that client on the road to change. This process necessarily requires the development of a therapeutic rapport and an understanding that the therapist is working in the best interest of the client. However, this essential aspect of effective psychological treatment has the potential to bias the therapist.

For example, the therapist who is overly invested in his/her treatment plan may misinterpret the plan as being more effective than it actually is. If treatment gains are not made, the therapist may project blame onto the client rather than question the plan itself or the therapist’s skill in implementing it. Likewise, a therapist who is overly invested in a client may become less critical of the client’s disclosures. S/he may misperceive the client’s gains and attribute setbacks to external sources. In other words, the process of providing therapy comes with the risk of developing bias.

This risk of bias is particularly problematic in forensic contexts where clients may have external incentives to be less than forthright with their therapists. For this reason, ethical guidelines state that therapists should not conduct forensic assessments of their clients (APA, 2013) and the Code of Conduct of the College of Psychologists of British Columbia (CPBC, 2014) explicitly states that psychologists “must avoid performing multiple and potentially conflicting roles.” Hence, reasonable concerns about a therapist’s ability to offer an unbiased view of their client must necessarily preclude a treating psychologist from offering an opinion reserved for an independent assessor.

This is not to say that therapists should have no input into an assessment, or cannot comment on the treatment progress, effort, and motivation of the client under evaluation. Indeed, therapists can be important collateral sources of information for independent assessors, which contributes to more accurate assessments and forensic decisions.

American Psychological Association (APA) (2013). Specialty Guidelines for Forensic Psychology. American Psychologist. 68(1), 7–19.
College of Psychologists of British Columbia (2014). CPBC Code of Conduct. http://www.collegeofpsychologists.bc.ca/docs/10.CPBCCodeofConduct.pdf