Magic One: The Senate Trial is GOVERNED by the Senate Rules... and so is the Chairman during the Trial (Justice Roberts). This isn't a Criminal trial. The Senate Rules allow any group of 51 Senators to overrule the Chairman (Roberts) on many issues (like who will be subpoenaed to testify and who will not).
If 51 (or more) Senators want to have Joe Biden, Adam Schiff, and Hunter Biden testify but the Chairman (Roberts) refuses, the Senators can overrule him and send the subpoenas and they WILL testify. Equally, if 51 Senators do NOT want someone to be subpoenaed to testify, they can quash the subpoena and stop them from testifying.
"If the Senate did end up conducting a trial, Rule VII gives Chief Justice Roberts control over procedural aspects of the trial, including issuing orders for specific people to testify and making decisions about disputed points of the law.
However, that same rule lets McConnell circumvent Roberts’ control, potentially in ways that could limit, or expand, the impeachment process. For instance, if the House members presenting the case wanted to subpoena a witness who might give evidence against Trump, senators could ask Roberts to block the subpoena. If he refused, they could overrule him, again by a simple majority in a Republican-controlled Senate.
McConnell could also use Rule VII to introduce into the trial new information that would be to Trump’s political benefit – such as asking Roberts to subpoena Joe Biden and his son Hunter, which could heighten the partisan divide, and distract or confuse the public about who is on trial for what. If Roberts declined, again the senators themselves could vote to issue the subpoenas."
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"Critically, and contrary to common mythology and parlance, the chief justice is not the “judge” in an impeachment trial. The Senate itself is both judge and trier of fact, and the chief justice serves as its presiding officer. The rules thus require the chief justice to direct “all forms of the proceedings” (Rule 7) and, in so doing, “to make and issue all orders, mandates, writs, and precepts authorized by the rules” (Rule 5)."
The Republicans hold the Senate Majority and can easily get 51 votes to overrule Roberts... with votes to spare.
