Expert witnesses in contested divorce cases can be utilized for almost every significant issue including custody, income verification, valuing assets such as real estate, business interests, financial accounts, retirement assets, tax consequences of the distribution of assets and the effect of tax deductions and tax filing status.
The selection of an expert can be made by the litigants or their attorneys or by the court. More often than not the parties agree to the selection of an expert and agree how to share the cost of the expert's fees. The expert is then considered to be a "neutral" so that there is no greater allegiance to one side or the other. Alternatively, each party may hire their own expert and then the question will be how to resolve the two reports if the experts arrive at different conclusions. For example a house appraiser that is hired by one person alone may be told to find the highest selling comparable homes while the other appraiser is asked to find the lowest selling comparable homes. Accounting experts who report on business values or income generation may also utilize different assumptions, different reference guides and different business predictions and generate reports that are significantly different. Therefore, often to avoid the expense of "battling experts" clients will agree to jointly retain a neutral expert so that there is one report that both sides will utilize.
Obviously, the expert should limit their opinion to the matters in which they have expertise. So the psychologist writing a custody report should not address the value of assets or suggest which person is telling the truth regarding the value of assets as those areas are outside the field of study of the expert. It would be like asking your doctor for tax advice.
The selection of experts should be done carefully and with thought in mind that they will be respected by both the attorneys and the court if called upon to testify. There is nothing worse than having an expert who at trial is found not to have the proper education, licensing or experience. Often the attorneys will know who are some of the most widely utilized experts in the various areas involved in the divorce case. Of course the expert needs to be able to write a report that can be understood and explained in a clear manner even if the subject is complicated.