The expert witness bears the responsibility for misleading testimony, but the courts are to blame for permitting it. The courts give experts privileges that make it possible for them to escape some of the constraints of giving evidence. This failure of the courts results from three main influences. First, the judges subscribe to invalid beliefs rather than validated knowledge. Second, they too easily accept labels, allowing tricks of classification to confuse the issues. Third, the courts fail to understand the logic of cause and effect in reaching fact-based conclusions. The core of this paper focuses on the latter influence. In the courtroom, experts properly offer their understanding of cause and effect. Provided they restrict their testimony to the knowledge of what has happened in real life, validated by observation and experiment, they do not mislead. In many court cases, expert witnesses and often the court reason backward from a partial presentation of facts associated with an effect to hypothesize about a cause. An incomplete knowledge of effects cannot produce certainty about the cause of known effects, and even a complete knowledge of effects cannot lead to certainty about causes. Neither can knowledge about two sets of facts necessarily produce valid reasoning about the cause-and-effect links of those facts. Reasoning from effect to cause has many pitfalls and must be carefully scrutinized by the courts. 14 references