Expertise is a tool that obtains and evaluates important evidence examined under the heading ofevidence. Expert is the person who assists the judge within the framework of his technical knowledgeor institution. The most important requirement for being an expert witness is to have specialknowledge. It is because the judge consults an expert on issues that he cannot solve with hisprofessional and technical knowledge. Expert is a vice-assistant of the judge but can never replace ajudge or function as a judge. Expert is just obliged to answer the questions that were asked to him.More intervention than that exceeds the limit of the duty of an expert. To sum up, in the situationswhich require expertise, special or technical knowledge; requesting the opinion of the expert could bedecided “sua sponte” , whereas the view of the expert can be decided by the request of the publicprosecutor, participant, the attorney or the suspect or the accused, attorney or legal representative. Thefirst rule to be put forward in this context is that expertise is an optional issue. As it is stated in thearticle text a judge "... can apply" to the expert. Application to an expert is not compulsory as a rule.The judge is responsible for issues that he/she can solve with his daily knowledge or professionalknowledge and experience and he is not allowed to apply to an expert. The thing that we alwayscriticize in our system, the fact that judges cannot specialize in a certain court and serve in differentcourts, is actually an advantage in this respect. However, it is accepted that the judge is already anexpert in all legal matters. This is why it is against the law for the judge to apply to an expert as anotherlawyer.