Dealing with expert opinions
<blockquote>
<p>Every Economist who is consistent with their discipline subscribes to
the subjective theory of value; <strong>how does a Judge who wants to be
consistent with Economics and coincidentally also is a B.A in
economics deal with an Expert Report that treats Value as Objective?</strong></p>
<p>Law frequently deals with value (the value of something; at what price
it would be bought or sold) but seems to take lightly the
philosophical depth of the concept of Value. It seems that a judge
should accept the expert opinion as is and can't consider its
methodology or philosophy. We just let the expert tell us what value
is without any thought. It is what it is.</p>
</blockquote>
<p>Above was the previous phrasing of the question. A more general phrasing would be</p>
<p><strong>How can a judge deal with methodological flaws in expert opinions?</strong></p>
<p>The above is an example when the expert says the Value of X item is Y but it can't actually be bought or sold at that price. The Judge may have personal expertise in the field of the expert opinion or it can be common knowledge. Do we just say expert opinions are what they are and we must accept at face value the least fallacious?</p>
<p>I am asking in the Context of how courts in Civil Law system appoint Experts.</p>

<p>The law does not deal with a judge who wants to be consistent with Economics and coincidentally also is a B.A in economics. The law just deals with judges, irrespective of their desires. The law simply tells the judge &quot;Follow the law&quot; – what constitutes following the law differs from jurisdiction to jurisdiction. This is so whether the issue is statutory interpretation or the determination of loss in a contract dispute, or some issue touching on the notion of &quot;profound injustice&quot;.</p>
<p>In the US, <a href="https://www.law.cornell.edu/rules/fre/rule_702" rel="nofollow noreferrer">this</a> is the basic rule regarding admissibility of expert testimony. It starts:</p>
<blockquote>
<p>A witness who is qualified as an expert by knowledge, skill,
experience, training, or education may testify in the form of an
opinion or otherwise if</p>
</blockquote>
<p>Then the court must decide whether a particular witness satisfies the conditions. The criteria are that the specialized knowledge will help the trier of fact, and is based on sufficient facts, and appropriate to your question</p>
<blockquote>
<p>(c) the testimony is the product of reliable principles and methods;
and</p>
<p>(d) the expert has reliably applied the principles and methods to the
facts of the case.</p>
</blockquote>
<p>Note that the sociology of a method is not an explicit component of this rule. In fact, voiceprint evidence is still admissible in many US jurisdictions although it has been thoroughly rejected in the scientific community. Evidence that is admitted which goes against the interests of one party is stiff defeasible under US law.</p>
<p>If a witness is to testify solely to a self-evident fact that is not disputed, the witness' testimony is irrelevant because it does not help the trier of fact.</p>

<h2>The judge considers the evidence presented and the law</h2>
<p><strong>Any judge that brings in evidence that neither party has contended is in error.</strong></p>
<p>In common law jurisdictions, the purpose of a lawsuit is to resolve the dispute between the parties using the evidence that the parties submit: the judge is not there to introduce things the parties don't submit.</p>
<p>If the parties agree that value is objective or that pigs can fly, then the court accepts that, for this case, those things are facts. If there is a dispute on these facts, then each side presents evidence that supports their position and on the evidence and only on the evidence, the judge decides which party has proved their position - a judge should not substitute personal knowledge for evidence.</p>
<p>Similarly, just because the current paradigm among economists is that value is relative or the paradigm among chemists is that fire is hot is irrelevant. Each side can introduce evidence (probably expert evidence) on the relativeness of value or the hotness of fire and where those experts disagree (as they invariably do), the judge decides whose evidence they prefer.</p>
<p>That does not mean that a judge who is an expert in another field cannot utilise their expertise but that should be constrained to asking the parties to bring evidence. For example: &quot;You guys are arguing on the basis the value is objective but you haven't submitted any evidence that the court should accept that premise, rather than the alternative that it's relative. Can you make submissions on this matter or agree that for this case you want the court to treat value as objective?&quot;</p>

evidence rules-of-court rules-of-evidence civil-legal-system