President Trump suggested the special prosecutor's team might not be fair, impartial investigators because of previous political contributions, legal clients and personal friends. (Meg Kelly/The Washington Post)

Since special counsel Robert S. Mueller III began his Russia investigation, Trump’s supporters have sought to impugn the probe’s integrity. Now some are accusing Mueller of ulterior motives after news broke that Mueller is using a grand jury in the District of Columbia in addition to the one already at work in Alexandria, Va. Like other attacks on the investigation, these charges are baseless.

Mueller’s critics allege he purposely chose a grand jury from a heavily Democratic area. Harvard Law Professor Alan Dershowitz has claimed that Mueller is turning to a D.C. grand jury to obtain a tactical advantage. Any resulting trials would take place in D.C., which, Dershowitz argues, “is always solidly Democratic and has an ethnic and racial composition that might be very unfavorable to the Trump administration” — in contrast, presumably, to whiter and more conservative Northern Virginia.

For his part, Newt Gingrich offered the following on Twitter:

President Trump got 68.63% in West Virginia, 4.8% in Washingtoin DC. Guess where Mueller has a grand jury? Guess how biased it will be? — Newt Gingrich (@newtgingrich) August 6, 2017

Such misguided claims are par for the course in an environment where everything is political, the motives of career professionals are routinely attacked, and any investigation is dismissed as a “witch hunt.”

Let’s begin with Gingrich, whose tweet is particularly ridiculous. The former House speaker apparently believes prosecutors are free to conduct grand jury investigations wherever they feel the environment might be politically favorable.

In the real world, a grand jury must have venue over the potential crimes it investigates. That means at least some part of the criminal acts must have taken place in the district where the grand jury is sitting.

The reason there is not a grand jury in West Virginia, or Texas, or any other state that Gingrich might prefer is that none of the matters being investigated took place there. Unless Gingrich knows something we don’t, West Virginia is completely irrelevant.

Dershowitz also ignores the venue issue. He assumes that anything Mueller is investigating could readily be prosecuted either in D.C. or in Virginia. I suspect that is not the case. Crimes such as filing a false security clearance form or failing to register as a foreign agent, for example, may take place entirely in D.C. Other acts potentially under investigation took place on Capitol Hill or in the White House and may lack the requisite ties to Virginia.

Dershowitz’s claims also betray a lack of familiarity with Justice Department practice in recent years. In many high-profile cases, if it does have a choice, the Justice Department — under both Democrat and Republican administrations — has often preferred the Eastern District of Virginia (Alexandria) to D.C.

The Washington Post's Carol Leonnig explains how President Trump and his lawyers are attempting to deflect special counsel Robert Mueller's investigation. (Victoria Walker,Peter Stevenson,Ashleigh Joplin/The Washington Post)

The Eastern District of Virginia is known for its “rocket docket” that moves cases along very quickly, which the prosecution usually prefers. Its judges are considered no-nonsense and not terribly sympathetic to criminal defendants. And Eastern District of Virginia juries often consist of law-and-order types sympathetic to the government and law enforcement.

But put aside such trial lawyer folklore. Fundamentally, this is a D.C. case. It involves potential foreign interference with our national government. Washington is the epicenter of all the events under investigation. It is the logical venue for almost any criminal charges that might result.

There’s no reason to believe Mueller’s move is anything other than a routine, appropriate step in his investigation. Sadly, that won’t stop critics who continue to disregard legal norms, assign political motives to every action and further erode respect for the rule of law.