Opinion of expert is relevent under the Evidence Act.

Yes.  Sec.45 to 47 of the Indian Evidence Act deals with the expert opinion.  The opinion of the expert is relevant.   But, the court is not bound by the opinion of the expert.  The court may or may not take into consideration the opinion of the expert while adjudicatinig the issue.  The Judge may take into consideration the opinion of the expert, but there is no absolute rule which make the Judge bound by the opinion of the expert.   I will try to get the citation in that regard. 

 section 45  to 51 of evidence act.  

Dear freinds, 

     Law of evidence allows a person - who is a witness to state the facts related to either to a fact in issue or to relevant fact, but not his inference. It applies to both criminal law and civil law. The opinion of any person other than the judge by whom the fact has to be decided as to the existence of the facts in issue or relevant facts are as a rule, irrelevant to the decision of the cases to which they relate for the most obvious reasons - for this would invest the person whose opinion was proved with the character of a judge. 

    The rule however, is not without its exceptions. "If matters arise in our law which concern other sciences or faculties, we commonly apply for the aid of that science or faculty which it concerns." The expert witness is, thus, an exception to the exclusionary rule and is permitted to give opinion evidence.         

      The Judge is not expected to be an expert in all the fields - especially where the subject matters involves technical knowledge. He is not capable of drawing inference from the facts which are highly technical. In these circumstances he needs the help of an expert - who is supposed to have superior knowledge or experience in relation to the subject matter. This qualification makes the latter's evidence admissible in that particular case though he is no way related to the case. Because an expert has an advantage of a particular knowledge vis-à-vis a judge who is not equipped with the technical knowledge and hence not capable of drawing an inference from the facts presented before him.