He has nothing to do with the impeachment trials.
It is the House and then the Senate with the Chief Justice as the judge.
The Vice-President does not preside at an impeachment of a President. The Constitution requires that the Chief Justice of the Supreme Court preside over an impeachment trial.
The VP does not preside because in the presidential line of succession if the President was removed, the VP would fill the role as president, meaning that the VP has enough motive to see the President removed from office.
when the president of the united states is tried, the chief justice shall preside
The Chief Justice of the United States presides over a US Presidential impeachment trial; an "Impeachment Trial Committee" comprising Senators selected by the Presiding Officer of the Senate* is in charge of all other impeachment trials. This practice began in 1986 when the Senate amended its rules and procedures for impeachment trials.* The Presiding Officer is not a fixed position. The Vice-President (currently Joe Biden), who also serves as President of the Senate, could be the Presiding Officer; or, in his (or her) absence, the President pro tempore (currently Daniel Inouye, D-HI) could preside; or, anyone the President of the Senate or President pro tempore designates -- even a Junior Senator -- could serve in that capacity.
Such is what the rules of the Senate say. The president of the Senate is the vice-president who would take the president's office if he were convicted. He would have a conflict of interest, to be sure. Also, it is good to have an experienced judge rule over such an important trial.
As President of the Senate, the U.S. Vice President presides over most impeachment trials. However, Article I, Section 3, Clause 6 of the U.S. Constitution specifies that when the President is on trial the Chief Justice of the Supreme Court presides. And although the Constitution doesn't say, I assume that would also be the case if the Vice President were the defendant in an impeachment trial (an incumbent U.S. Vice President has never been impeached to date).
If the Senate tries the Chief Justice, it would follow the procedure used in most impeachment trials. The presiding officer of the Senate or an appointed "Impeachment Trial Committee" would preside, or act as judge, and the other Senators would serve as the jury.This procedure is used for the removal trial of allofficials except the US President, and became legal practice in 1986 when the Senate amended its rules and procedures for impeachment trials. The Chief Justice of the Supreme Court only presides over the impeachment trial of a US President.
The Chief Justice of the United States presides over an impeachment trial of the president. This role is specified in the Constitution, as the Chief Justice ensures that the proceedings are conducted fairly and according to the rules. The Senate serves as the jury in the trial, and a two-thirds majority is required for conviction.
The Chief Excecutive
Congress
impeachment
Such is what the rules of the Senate say. The president of the Senate is the vice-president who would take the president's office if he were convicted. He would have a conflict of interest, to be sure. Also, it is good to have an experienced judge rule over such an important trial.