Why *must* a defendant be present during a criminal trial?
<p>The <a href="https://www.law.cornell.edu/constitution/sixth_amendment" rel="nofollow noreferrer">Sixth Amendment</a> guarantees:</p>

<blockquote>
  <p>In all criminal prosecutions, the accused shall enjoy the right to a speedy and public trial, by an impartial jury....</p>
</blockquote>

<p>I recently discovered that, in general, these "rights" are <em>not optional</em>!</p>

<p>For example, under under Federal rule: if you want a bench trial in a criminal matter, both the prosecution and the judge must agree to waive the jury (<a href="https://www.law.cornell.edu/rules/frcrmp/rule_23" rel="nofollow noreferrer">FRCP 23a</a>).  (Many states do, however, allow a criminal defendant to unilaterally opt for a bench trial.)</p>

<p>Likewise: Under <a href="https://www.law.cornell.edu/rules/frcrmp/rule_43" rel="nofollow noreferrer">FRCP 43</a>, a criminal defendant <em>cannot</em> opt out of being present for his entire trial.</p>

<p>These rules seem opposed to the basic civic principles that surround the presumption of innocence before conviction, and the right of a person to pursue an effective defense.  I can think of plenty of reasons why a person may not want to show his face in a public court, much less sit through the entire process.  Including reasons that may prejudice the triers of fact: e.g., disfigurement, handicaps that produce irritating tics, etc.</p>

<p>The notes on these federal rules cite a great deal of jurisprudence and history.  Before I attempt my own research, can anyone point to principles or customs that might illuminate or reconcile these FRCP mandates with the basic understanding of American criminal justice I described?</p>

<p><a href="https://en.wikipedia.org/wiki/Trial_in_absentia#United_States" rel="noreferrer">SCOTUS has at least three times found that it is necessary for a defendant to be present at the beginning of a criminal trial in order to satisfy the Constitutional mandates regarding due process</a>.</p>

<p>So the simple answer is that <strong>a defendant <em>must</em> be present during a criminal trial because <em>without his presence no trial can begin</em></strong>.</p>

<p>However, once a trial has begun <a href="https://www.law.cornell.edu/rules/frcrmp/rule_43" rel="noreferrer">FRCP Rule 43</a> itself (section c) allows for the absence of the defendant.  Among the provisions: The defendant can waive his <em>right</em> to be present simply by voluntary absence.  The defendant can also waive his right by disruptive behavior in the court.</p>

<p>Here on Law SE, we can answer questions about what the law is. We cannot be so eager to answer <strong>why</strong> it is what it is.</p>

<p>While the basic purpose of the right to be present during trial, and to have a jury trial, is to protect the defendant, other purposes may be served as well. In particular, it is often said that a jury may and should evaluate the appearance and expressions of the defendant, just as they do with witnesses. Obviously they cannot do this if the defendant is absent.</p>

<p>I don't know why a defendant must obtain the consent of the prosecution for a non-jury trial, particularly when the rule is otherwise in many states.  But there is no constitutional right to a non-jury trial. If Congress chose to abolish bench trials in all Federal cases, it could. Therefore this rule is also constitutional. </p>

<p>Similarly there is no constitutional right to be absent during a trial.</p>

<p>I think it's because defendants could avoid trial to prevent identification, or to otherwise improperly disrupt the course of the proceedings:</p>

<blockquote>
  <p>Despite some earlier authority to the contrary, courts now agree that
  the right to be present guaranteed by the federal constitution can be
  waived or forfeited in capital, as well as non-capital, cases.</p>
  
  <p>Although a defendant can waive his right to be present at his trial,
  he does not have a constitutional right to insist upon his absence.
  For, as the Supreme Court explained in <em>Singer v. United States</em>, “[t]he
  ability to waive a constitutional right does not ordinarily carry with
  it the right to insist upon the opposite of that right.” A trial court
  therefore can order a defendant’s personal appearance, despite his
  desire to stay away from the trial, whenever his presence is necessary
  to conduct the trial properly, such as where the prosecution
  contemplates having one of its witnesses make an in-court
  identification of the accused.</p>
</blockquote>

<p>3 David S. Rudstein, et al., <em>Criminal Constitutional Law</em> § 14A.02 (2018) (citations omitted).</p>

united-states criminal-law trial sixth-amendment legislative-intent