Why can&#39;t a party raise new arguments in United States court of appeals?
<p>In the <a href="https://www.eff.org/files/2014/04/16/lavabit_opinion.pdf" rel="nofollow noreferrer">Lavabit judgement</a>, I saw this:</p>

<p>see also <strong>Agra, Gill &amp; Duffus, Inc. v. Benson</strong>, 920 F.2d 1173, 1176 (4th Cir. 1990) <em>("We will not accept on appeal theories that were not raised in the district court except under unusual circumstances.")</em>.</p>

<p>Of course it justifies why the rule is applied for this case, but what is the original reason this rule was applied?</p>

<p>This is largely congruent with* the doctrine of <a href="https://en.wikipedia.org/wiki/Laches_%28equity%29" rel="noreferrer"><em>laches</em></a>.  The basic idea, under common law, is that you can lose rights by failing to assert them.  This is generally important for many reasons, but specifically in the case of appeals:</p>

<ul>
<li>The argument should have been brought before the trial court.  Justice is not a game, but it's important to recognize that the party trying to raise the argument had an opportunity to do so already.  They have given up their right to raise this argument, and extending them the <em>privilege</em> of doing so is (for the following reasons) not good for the system.</li>
<li>Courts of appeals are typically not well-equipped to evaluate factual evidence.  It is not their area of expertise.  Witnesses or evidence may be less available.  It's just not practical to try to adjudicate factual issues on appeal, most of the time.</li>
<li>If anyone could get an appeal by bringing new factual arguments, then <em>everyone</em> would do that.  You'd bring your strongest argument before the district court, and then if that fails, bring the second strongest before the circuit court.  That way, you get an extra trial.  This is inefficient.</li>
<li>Allowing factual arguments on appeal would encourage attorneys and their clients to strategically bring different facts before different courts.  This kind of forum-shopping is harmful because it has little to do with who has the stronger overall case, and more to do with who has the better lawyer.</li>
</ul>

<p>* "Congruent with" is not the same as "an instance of"; this rule is <em>not</em> formally an application of <em>laches</em>.  It just happens to share the same justification.</p>

<p>There are two types of <a href="http://en.wikipedia.org/wiki/Standard_of_review#De_novo" rel="noreferrer">appeals.</a> Under de novo appeals, the facts are questioned, in which case it is possible to raise new (factual) arguments, almost as if the first proceeding had never taken place.</p>

<p>Most appeals are appeals on the record, which means that only the application of the law is being appealed. Under these circumstances, the facts (as found by e.g. a jury) cannot be challenged, and therefore new (factual) arguments can't be raised, only legal arguments.</p>

<p>In the United States, appeals are generally <em>appeals on the record</em>. The only thing that can be challenged is <em>process</em>; that is, appeals must contend that there was something <em>unfair or incorrect</em> about the process of the original proceeding. </p>

united-states rules-of-court