In recent days, there have been demands on Twitter and elsewhere from people who want Trump's family, friends, courtiers, and other enablers called now to testify under oath in public hearings in Congress. These folks, including the ACLU, want to hear now - right now! - about Trump's alleged collusion with Russia during the campaign (and, perhaps, before and after it).

Instead, so far, key witnesses like Jared Kushner have given, or are scheduled to give, statements and interviews in closed meetings with investigators and members of the Senate and House committees with investigative mandates from their respective chambers.

Complete transparency in the Russia-collusion investigation is vital to the public's understanding of where we are, how we got here, and how we prevent further attacks on our institutions from white supremacists and oligarchs, whether foreign or home-grown. Convictions and substantial prison sentences are also essential, for anyone who committed state or federal crimes to deliver the presidency to Mr. Trump, as deterrence against future crimes.

That said, it's too early to require public sworn testimony now from certain witnesses, especially those who are in or were formerly in Trump's inner circle. Open-hearing sworn testimony at this time might impair our ability to find out what happened and prevent it from happening again. Worse, sworn testimony in open hearings might block or nullify efforts to punish any criminal actors, even before Mr. Trump pardons or attempts to pardon anyone.

We can take our cues on this issue from the progressive members of the Congressional committees engaged in the Russia-Trump collusion investigation. By and large, they don't appear to be complaining forcefully about closed committee interviews with witnesses. As they aren't complaining, we probably don't need to press the issue of public sworn testimony, though continuing demands from some quarters usefully keep the issue of collusion prominent in the media.

Those progressive Congressional committee members are vigilant. Think of John Lewis and Elijah Cummings during the various House Benghazi investigations, excoriating their process and substance. Think of Adam Schiff and Eric Swawell on the House Intelligence Committee repeatedly airing objections to the conduct of the Committee's chairman, Devin Nunes. In contrast, note the absence of complaints from ranking Democrat Mark Warner - so far - about the conduct of the Senate Intelligence Committee.

For the moment, we can even tolerate the relative amity between Dianne Feinstein and Chuck Grassley on the Senate Judiciary Committee. (Their cooperation might be short-lived, however, given Grassley's continuing interest in manufacturing a Democratic scandal from the Trump-Russia investigation via an investigation of the leaks that have illuminated it.)

There are a couple of easy explanations for the relative acquiescence of leading Congressional Democrats in most - but not all - of the current Congressional inquires. First, Democrats don't control the committees; they're the minority. They have to negotiate and cajole their way to progress in the investigations. Second - and this is more important - to the extent that they appear content with the course of the investigations, it might be because they actually are content, especially with respect to the investigations' coordination of activities with Special Counsel Robert Mueller.

If we want to see criminal prosecutions and convictions of anyone guilty of federal crimes in the Trump-Russia collusion inquiry, Congress should stay out of the way of the Special Counsel. If Congress now insists on public sworn testimony from any of the key investigative targets, they might make Mueller's work more difficult, if not impossible.

To understand this, look back at the Iran-Contra investigation during the second Reagan term. Lawrence Walsh, the Independent Counsel, obtained convictions of Oliver North and John Poindexter for their roles in selling arms to Iran to get funds for contras in Nicaragua. (By the way, the first President Bush pardoned several of the conspirators in this scheme.)

Before their convictions, however, North and Poindexter were granted "use immunity" by Congress in exchange for their agreement to testify about their conduct in Iran-Contra. "Under a grant of use immunity, the actual testimony given by the witness cannot be introduced as evidence against him, but evidence derived from that testimony can be. The witness can still be convicted for the crimes mentioned in the testimony on the basis of other evidence."

However, the convictions of North and Poindexter were overturned because their immunized sworn Congressional testimony might have tainted their trials.

There are, however, limits to the protection afforded by use immunity. As explained here,

Under a use immunity grant, the prosecutor is forbidden from entering into evidence the fact that the witness confessed to the crime during his compelled testimony. A transcript of that testimony is inadmissible in evidence. However, the prosecutor is free to hear or read the testimony himself while investigating the case. After learning about the location of the gun from the compelled testimony, the prosecutor could have police retrieve the gun and submit it as evidence at the witness’s trial.

Attorneys representing witnesses invited to testify voluntarily to Congress in the Russia-collusion investigation probably will ask for use immunity for their clients. If they don't get use immunity for their clients, they may advise their clients to refuse to appear voluntarily. If the witnesses are then compelled by subpoena to testify under oath, the clients may invoke the 5th Amendment to avoid self-incrimination and say nothing, thus shedding no light on what happened in the Trump campaign in relation to Russian interference in the 2016 election.

As to witnesses who get use immunity, Special Counsel Mueller may not use their testimony as direct evidence of any criminal conduct in any prosecution. That these early witnesses are giving interviews in private and Congressional Democrats aren't complaining very loudly or at all suggests that they aren't being offered use immunity. Indeed, it wouldn't be surprising if the Democrats started objecting if the Congressional committees began offering use immunity to witnesses in exchange for their public-hearing sworn testimony without the consent of the Democratic minorities on the committees.

So, we should keep in mind the context of these Congressional investigations before we demand sworn testimony now in public hearings by figures who've been identified as communicating with Russians related to the 2016 presidential campaign. If Democrats retake control of the House and Senate in 2018 - the real goal at which we should aim - we'll find out everything we want to know about collusion with the Russians.

Until then, we might be served best by taking our cues from the progressive Democrats on these Congressional committees. If they are quiet, then Robert Mueller probably is busy - productively busy.