Speaker Pelosi is on something of a victory lap, hailing in New York magazine the indictments against President Trump as “exquisite,” not to mention “beautiful and intricate.” As to the January 6 charges, though, Mrs. Pelosi’s preening underscores the dubious origin of the case against Mr. Trump. That’s because the indictment arose via a committee of the legislature, a breach of the constitution’s separation of powers — and its ban on attainder.

In lay terms, that’s a “trial by legislature” — which the January 6 Committee undertook, helped by 14 ex-federal prosecutors, then passed the information along to the Justice Department. Federal prosecutors took the material and used it as the basis of their indictment of Mr. Trump for his actions on and before January 6. A legal doctrine known as the Fruit of the Poisonous Tree suggests this evidence is not valid to use in Mr. Trump’s trial.

Jack Smith’s indictment of Mr. Trump over January 6 “closely tracks the select committee’s work and findings,” New York explains, “presenting a factual narrative that traces — almost identically — the evidence presented” by the January 6 committee. They both outline what New York calls “a sophisticated, multipronged effort by Trump to remain in power that culminated in the mayhem at the U.S. Capitol.”

The former speaker, in her interview, was, New York reports, “reluctant to take any sort of credit for the committee’s work or Trump’s indictment.” Yet it’s not hard to connect the dots. Of Mr. Trump, Mrs. Pelosi says, “I knew on January 6 that he had committed a crime.” She makes clear she formed the committee as an instrument to confirm her deduction, praising its appointees for their “beautiful balance” and “seriousness of purpose.”

Plus, as New York observes, the Justice Department’s indictment of Mr. Trump over the Capitol riot might never have come about absent the January 6 Committee’s efforts. The interview points to a Washington Post account suggesting that there was foot-dragging on the part of Attorney General Garland and that when Justice moved, “it felt as though the department was reacting to the House committee’s work” and its press coverage. 

Of the account in the Post, Mrs. Pelosi merely tells New York that it did not come as “a complete shock or surprise.” No wonder, then, that Mr. Smith’s rush to prosecute Mr. Trump in time before the 2024 election required relying on the findings of the January 6 Committee. This could prove to be a gift to the former president’s legal defense, however, if they are able to demonstrate that the panel’s work represents an unconstitutional attainder. 

We understand this is a long shot, but we’re sticking with it. No less a figure than Chief Justice Warren has explained that the Framers sought to bar such behavior by Congress. They did so, he wrote, as “a general safeguard against legislative exercise of the judicial function.” The British monarchy used bills of attainder to punish individuals without trial. This is why, Warren noted, the Framers limited legislators “to the task of rule-making.”

Mark, too, that when the validity of the January 6 Committee was challenged in federal court — that happened in a dispute over a subpoena by the January 6 Committee to the Republican National Committee — the January 6 Committee decided to withdraw the request rather than risk being rebuked by a constitutional court. The challenge to the committee related, in part, to whether it lacked a proper legislative purpose.

The RNC had asked the riders of the District of Columbia Circuit of the United States Court of Appeals to weigh a “fundamental” question: whether the committee was “validly exercising the legislative power at all?” When the committee withdrew its subpoena request, the riders noted it “deprived us of the ability to review” some “important and unsettled constitutional questions.” The riders may yet get their chance in United States v. Donald Trump.