While procedures vary from state to state, the COVID-19 pandemic has substantially delayed criminal trials throughout the country. Plea bargaining has become even more prevalent than before. And the pandemic has put defendants' constitutional rights in tension with each other, as the right to a speedy trial has come into conflict with the right to a jury trial and the right to confront witnesses.
This latter right is based in the Confrontation Clause of the Sixth Amendment, which provides that "In all criminal prosecutions, the accused shall enjoy the right...to be confronted with the witnesses against him." The constitutionality of video testimony has come up before, but the pandemic has made this issue particularly important. The prevailing view is that, in most situations, video testimony violates the Confrontation Clause. But this view largely rests on an uncompelling, undertheorized version of originalism. And it reflects courts' ongoing difficulties with applying the Constitution to novel technologies.
In 2004's Crawford v. Washington, the Supreme Court adopted a largely originalist framework for the Confrontation Clause, requiring in-person confrontation at trial except when the witness is unavailable and the defendant has had a prior opportunity for cross-examination. Although Crawford didn't consider video testimony, the Supreme Court had a few years prior rejected a proposed amendment to the Rules of Criminal Procedure that would have allowed for video testimony in court in certain circumstances. Justice Scalia wrote separately, noting that he "shared the majority's view that the Judicial Conference's proposed [rule] is of dubious validity under the Confrontation Clause" and affirming that the Confrontation Clause required physical, in-person confrontation at some point. Between this rejection and the explicitly originalist approach of Crawford, the Court appears to have adopted Scalia's framework.
Yet the textual grounding for this approach is shaky. Justice Scalia wrote in a prior case that "'to confront' plainly means to encounter face-to-face." Does it? Scalia reads meaning into the Sixth Amendment that may not be there. There was no possibility in 1791 of effective confrontation other than through physical presence. The mere phrase "to  confront" in this context conveys nothing about whether video confrontation is sufficient. The text is ambiguous on this point.
But wait, you say, surely it's true that the original referent of "confront" was an in-person meeting, and this excludes the possibility of video confrontation. Yet the Court, and originalists everywhere, have squarely rejected this move in other contexts. In District of Columbia v. Heller, Justice Scalia writing for the Court rebuffed the argument that the "arms" referred to in the Second Amendment could be limited to the types of arms available in 1791. He went on to say that "speech" in the First Amendment and "searches" in the Fourth Amendment are concepts that expand to encompass digital technologies far outside founding-era understandings. On the other hand, Justice Scalia has argued that concepts like "cruel and unusual" are frozen in time as of the ratification of the Eighth Amendment. And the Court has ruled that the concept of a "felon" must only refer to those felonies in existence at the time of the ratification of the Fourth Amendment. Of course, in other Fourth Amendment cases the Court has done the opposite, ruling that a "felon" can change for constitutional purposes as modern legislatures add criminal statutes.
The inconsistency with which the Justices have treated changing contexts and technologies in originalist opinions suggests that this is essentially a toggle switch that judges can flip to reach a preferred outcome. There is no stable principle by which the Court addresses these issues. And there is no reason to think that the Sixth Amendment speaks at all to whether video confrontation sufficiently vindicates the confrontation right.
What we do know is that the crux of the confrontation right, both historically and practically, is cross-examination. The point was to avoid the conviction of defendants based on unreliable written affidavits, a practice sometimes abused by English authorities. So long as video testimony allows for effective cross-examination, it likely does not violate the Sixth Amendment. And even if video cross-examination is not 100% as effective as in-person cross-examination, that may be mitigated by the fact that video accusation is likely not as effective as in-person accusation either. The defendant may still benefit on net - and that's before we consider the benefits of a speedy trial, avoidance of health risks, and other compelling interests such as protecting victimized children.
Finally, another supposed downside of video testimony may actually enhance the accuracy of trial. Video testimony can make it more difficult for a jury to assess a witness's demeanor, forcing jurors to depend more on the content of the testimony rather than the apparent credibility of the witness. But as Dan Simon has pointed out, jurors are likely very poor at assessing witness credibility through visual cues. In any event, the use of deposition transcripts at common law indicates that the visual assessment of witnesses is not central to the confrontation right.
In the end, requiring in-person confrontation of witnesses might be good policy, or might benefit defendants more than prompt adjudication. But there is little reason to think that formal considerations compel us to reject video testimony - especially in a pandemic.