The medical expert witness testimony is a key moment in the pathway of patient complaints as well as in the line of defense of the defendant-physician. For the defendant, it is a difficult time, often experienced as humiliating, because his or her competences are questioned, appraised and discussed in public. However, the defendant must perceive and use this encounter as an opportunity to express his/her viewpoint on the medical accident. This article provides the principal juridical rules that govern the medical expert witness testimony that must be known, as well as some practical advice on how the medical expert witness testimony evolves and how to protect oneself from the complaints, In order to enable the defendant to best prepare for this confrontation between the involved parties.