After 18 months of investigating Donald Trump’s drive to overturn his 2020 election loss, the House committee on the January 6 insurrection has provided the Department of Justice with an exhaustive legal roadmap as it pursues potential criminal charges against the former US president.

Amid reports the committee is already co-operating with DoJ by sharing evidence garnered from 1,000 witness interviews and thousands of documents, former federal prosecutors say the panel’s work offers a trove of evidence to strengthen the formidable task of DoJ prosecutors investigating the former US president and his top loyalists.

The wealth of evidence against Trump compiled by the panel spurred its unprecedented decision to send the DoJ four criminal referrals for Trump and some top allies about their multi-track planning and false claims of fraud to block Joe Biden from taking office.

Although the referrals do not compel the justice department to file charges against Trump or others, the enormous evidence the panel amassed should boost its investigations, say ex-federal prosecutors.

The massive evidence assembled by the panel was the basis for accusing Trump of obstruction of an act of Congress, inciting insurrection, conspiracy to defraud the US and making false statements

“The central cause of January 6 was one man, former president Donald Trump, who many others followed,” the committee wrote in a detailed summary of its findings a few days before the release of its final 800-plus-page report on Thursday.

The panel’s blockbuster report concluded that Trump criminally plotted to nullify his defeat in 2020 and “provoked his supporters to violence” at the Capitol with baseless claims of widespread voter fraud.

Former prosecutors say the committee’s detailed factual presentation should boost some overlapping inquiries by DoJ including a months-long investigation into a fake electors scheme that Trump helped spearhead in tandem with John Eastman, a conservative lawyer who was also referred to the justice department for prosecution.

“The January 6 committee’s final hearing and lengthy executive summary make out a powerful case to support its criminal referrals as to Trump, Eastman, and unnamed others,” former DoJ inspector general Michael Bromwich told the Guardian.

“Although the referrals carry no legal weight, they provide an unusual preview of potential charges that may well be effective in swaying public opinion,” Bromwich said.

Daniel Richman, a former federal prosecutor who is now a professor at Columbia Law School, also said the panel’s work should have a positive impact on the DoJ’s investigations.

“Although the committee’s hearings gave a good preview of the criminal liability theories it has now laid out in its summary, the new [executive summary] document does an extraordinary job of pulling together the evidentiary materials the committee assembled,” Richman told the Guardian.

“The committee’s presentation goes far beyond a call for heads to roll, and amounts to a detailed prosecution memo that the DoJ will have to reckon with.”

Other former prosecutors said they agreed. “It is difficult to imagine that the DoJ could look at this body of facts and reach a different conclusion,” said Barbara McQuade, a former US attorney for eastern Michigan.

“Although the committee’s referral to the justice department is not binding in any way, and the DoJ will make its own independent assessment of whether charges are appropriate, the most important parts of the report are the facts it documents.”

That factual gold mine has caught the eye of special counsel Jack Smith, who attorney general Merrick Garland tapped last month to oversee the DoJ’s sprawling criminal inquiries into the January 6 insurrection.

Smith, on 5 December, in a letter, asked for all of the committee’s materials related to its 18-month inquiry, as Punchbowl News first reported.

After receiving the letter, the panel sent Smith’s team transcripts and documents, much of it concerning Eastman’s key role in promoting a fake electors scheme in tandem with Trump and others to block Biden’s certification by Congress.

The House panel has also provided the DoJ all of former White House chief of staff Mark Meadows’ text messages and other relevant evidence.

The committee has also shared transcripts of several witness interviews related to the fake electors ploy, plus the efforts by Trump and his loyalists to prod Georgia and some other states that Biden won to nullify their results.

According to a Politico report, the transcripts the panel sent to the special counsel included interviews with several top Trump-linked lawyers such as former vice-president Mike Pence’s top legal counsel Greg Jacob, former White House counsel Pat Cipollone, former attorney general Bill Barr, Jeffrey Rosen, who succeeded Barr as AG, and Rosen’s deputy Richard Donoghue.

Still, there are potential downsides to some of the evidence that the panel has made public in its extensive inquiries, say former prosecutors.

“The enormous cache of evidence developed by the January 6 committee is a mixed blessing for the DoJ,” Bromwich said. “Although it undoubtedly provides evidence that the DoJ had not yet collected or developed, it will require time and resources to master and fully grasp its significance.”

“More importantly, it may contain landmines of various kinds – for example, witnesses whose public testimony was powerful and unequivocal, but whose initial testimony was incomplete, misleading or false. That doesn’t matter in the context of a Congressional investigation; it matters a lot when a prosecutor needs to decide whether a witness will be vulnerable to attack on cross-examination based on the full body of their testimony.”

Other former prosecutors say the panel’s exhaustive documentation and witness transcripts should on balance benefit the special counsel.

“The committee report gives the special counsel not only the benefit of knowing what certain witnesses will say, it also lets him know what other witnesses won’t say,” Michael Moore, a former US attorney in Georgia, told the Guardian. “That type of intel gives him the ability to put together a stronger case with fewer surprises. More information is never a bad thing to a good lawyer.”

On the broader legal challenges facing the DoJ, ex-prosecutors say the panel’s work should goad the department to work diligently to investigate and charge Trump and others the panel has referred for prosecution.

“Normally, the department quietly exercises enormous discretion by hiding behind the mantra that it will pursue cases whenever the facts and law support doing so,” Richman said. “The public usually has to take its word for that, as it lacks the granular knowledge to make its own assessment.

“Here, though it may disagree with the committee’s handling of the law and the evidence, there will be considerable pressure on the DoJ to either bring the specified cases or find a way to explain why it will not.”