The House impeaches, it does not indict. Impeachment is a political process, not a legal one.
Let me speak more clearly, a House impeachment is tantamount to an indictment for trial in the Senate. The actual trial occurs in the Senate with the Chief Justice presiding.
Article 1, Section 2, Clause 5--"The House of Representatives . . . shall have the sole power of impeachment."The power of impeachment translates into the power to indict. The House, through the Judiciary Committee, conducts investigation and gathers evidence. At the proper time, the House assembles the evidence into individual indictments or charges known as Articles of Impeachment. Each article requires a majority vote of the House to pass to the Senate. Once impeached, the officer is on trial.
Article 1, Section 3, Clause 6--"The Senate shall have the sole power to try all impeachments.
When sitting for that purpose, they shall be on oath or affirmation. When the President of the United States is tried, the Chief Justice shall preside: And no person shall be convicted without the concurrence of two thirds of the members present."
The trial of the impeached officer is held in the Senate. In Nixon v. US, regarding the impeachment trial of a Federal judge, the Supreme Court ruled that the application of the phrase phrase "sole power to try all impeachments" to a particular case was not justiciable. In other words it held that the proper application of this constitutional language to a specific impeachment proceeding was not a question for the courts. Therefore, the process and procedure for impeachment lie solely within the purview of the legislature. The officer subject to an impeachment proceeding has no appeal to a federal court.
Article 1, Section 3, Clause 7--"Judgment in cases of impeachment shall not extend further than to removal from office, and disqualification to hold and enjoy any office of honor, trust or profit under the United States: but the party convicted shall nevertheless be liable and subject to indictment, trial, judgment and punishment, according to law."
An impeachment and removal does not activate the double jeopardy clause of the Fifth Amendment. The ex-officer may face criminal indictments and trials for the same conduct that led to their impeachment and removal from office.