Unconscious biases have been a hot topic for decades and have found their way into arbitration. While the decision-making process of arbitrators has been the focus of attention, there is hardly any legal literature that deals with potential biases of counsel. Psychological studies have identified a general overconfidence bias in counsel that can have a negative impact on case assessments. As a solution to this issue, a recent study of 2018 showed how to use de-biasing techniques and how this improved case assessments: analysing almost 500 law students in the United States, the study demonstrated how overconfidence and self-serving judgments of fairness could tamper with the ability to assess the value of a case when the students were required to represent a client’s interests. This effect is called ‘partisan bias’. The study displayed its effect on specific case valuation methods and demonstrated how it could be partly eliminated by a de-biasing technique called ‘consider the opposite’. Further, the study showed that individuals with a high score of a need for cognitive closure, i.e., a motivational tendency to prefer clear answers over ambiguity, were more inclined to be susceptible to partisan bias, however were equally likely to be receptive to de-biasing.