There is now powerful evidence that Donald Trump committed impeachable offenses by using his foreign policy and military powers to solicit (and all but coerce) Ukraine’s president to interfere with the 2020 presidential election. Nancy Pelosi, speaker of the House of Representatives, has confirmed that the House will move swiftly to investigate this threat to democracy, national security, and the separation of powers.

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The first stages of that impeachment inquiry are already under way. It’s therefore important to think ahead about what should happen as the House inquiry unfolds – especially in the House intelligence and judiciary committees, chaired respectively by Adam Schiff and Jerrold Nadler. If the House is going to impeach the president, it better have a plan.

This may seem obvious, but it’s easy to lose sight of the bigger picture. Each passing day brings new revelations about the depth of Trump’s abuses, and the involvement of senior officials in fomenting or concealing them. Trump and his allies have responded by seeking to daze and disorient the public; they apparently hope to gaslight their way past high crimes and misdemeanors. With so many fires being set, attention is focused on the latest breaking news.

Moreover, talk of congressional strategy and procedure is boring. That’s true even for law professors like me. It’s one thing to believe that impeachment is necessary; it’s quite another to think about how the House will carry it out.

But here, process is profoundly important. As Joshua Matz and I explain in our book, To End a Presidency: “Procedure is where romantic ideas about legislators as the voice of the people collide with institutional reality. Good process is crucial to making thoughtful, accurate, and legitimate decisions. It’s through these rules that Congress evaluates the evidence and structures its deliberations … Impeachments must therefore be fair and appear fair.”

First and foremost, that means undertaking a thorough investigation. The House cannot make a reasoned judgment about whether to impeach – and what to include in articles of impeachment – without a clear understanding of what exactly Trump (and those in his orbit) did wrong. And there is clearly much more to this story than is yet known publicly.

Don’t get me wrong: we already know a lot from the rough transcript of Trump’s call with Ukraine’s president, the whistleblower complaint, Trump’s public statements, and credible news reports. That information alone supports a powerful case for impeachment. At minimum, it shifts the burden to Trump to disprove the obvious inference that he abused power, violated his oath, betrayed the nation, and acted corruptly.

Facebook Twitter Pinterest Adam Schiff , chair of the House intelligence committee. Photograph: Leah Millis/Reuters

But the House, and particularly the intelligence committee (which is expert in these matters), must probe further. Principles of due process require that Trump and other officials be afforded a meaningful opportunity to tell their story under oath. However unlikely, it is at least conceivable that they will offer context which casts the public record in a different light. At the same time, there is evidence that Trump’s abuses rippled out in many directions. Even as it weighs Trump’s fate, the House is duty-bound to examine any possible threats to national security and fair elections.

So the House must investigate – and must do so quickly. This presents its own dilemma. Trump has spent the past year “fighting all the subpoenas” with bogus legal arguments meant to justify near-total defiance of Congress. The House has gone to court to compel compliance with its subpoenas, but judicial process can take months or years. If Trump persists in such tactics, he could deny the House access to key witnesses and testimony, or could string the House along while pretending (in bad faith) to negotiate.

Given the urgency of the situation, the House has no choice but to issue a firm ultimatum to Trump: comply with our subpoenas immediately or we will infer that your unlawful obstruction is itself proof of guilt. This is well within the House’s authority. When the House opens an impeachment inquiry, it wields extraordinary constitutional powers and serves as the ultimate check on a rogue president. It can therefore overcome virtually any executive branch privilege or immunity. Otherwise, the president could commit high crimes and misdemeanors and defeat accountability by simply defying all efforts to discover his wrongdoing.

The House has already embarked on this path. On Friday, the House foreign affairs committee, in consultation with the House intelligence and oversight committees, issued a first round of subpoenas – and made clear to recipients that “your failure or refusal to comply with the subpoena shall constitute evidence of obstruction of the House’s impeachment inquiry.” That is exactly the right procedure.

Over the coming weeks, the House will presumably serve many more subpoenas. If the executive branch lawlessly refuses to turn over evidence demanded by the House, that will be impeachable obstruction of Congress and further proof of Trump’s guilt. If evidence is turned over and tends to confirm that Trump abused his office, the House will need to move quickly toward articles of impeachment.

That’s where the judiciary committee comes in. Under the House rules – and consistent with the Richard Nixon and Bill Clinton precedents – the judiciary committee takes a lead role in the impeachment process. That makes sense, since any impeachment raises a host of complex constitutional and legal questions, and the judiciary committee is uniquely equipped with the expertise, experience, and staff to help the House navigate those challenges most effectively.

As the intelligence, foreign affairs and oversight committees investigate, the judiciary committee must set to work. It may wish to hold hearings on three sets of issues: first, the final factual conclusions reached by other committees that bear on impeachment; second, the many legal and constitutional judgments involved in deciding whether to impeach (and on what specific grounds); and finally, how the Ukraine issue might relate to other instances of self-dealing, obstruction, and abuse already under investigation. The judiciary committee has already adopted procedures for impeachment hearings and can use them here (including a mechanism for allowing Trump to respond to its findings).

Eventually, if impeachment is warranted, the judiciary committee – acting closely with the other investigating committees – will need to produce a detailed factual and legal report making that case, along with specific proposed articles for the House to vote on. The judiciary committee report recommending articles of impeachment against Nixon is one of the great works of constitutional law of the 20th century.

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They should follow that model here, both to present the strongest possible case to the public and the Senate and also to document for history the record of Trump’s outrageous misconduct. But it will have to do so expeditiously. Time is not the friend of this indispensable effort to hold a renegade president properly to account – and to protect the republic from his continued and seemingly escalating abuses.

The months ahead will be trying. Trump will pull out all the stops as he fights for his political life. But the impeachment power was built for moments like this one. It exists to guard against would-be tyrants who sacrifice democracy and sell out national security to advance their private self-interest, especially when they embroil foreign nations in that corrupt effort. The House must invoke that power wisely and decisively as it investigates Trump’s misconduct – and decides how best to activate our constitution’s ultimate safeguard.

• Laurence H Tribe is professor of constitutional law at Harvard Law School