The disclosure that Special Council Jack Smith plans to call at trial an expert who harvested data from President Trump’s cellphone throws into sharp relief a prosecution that is quickly getting hi-tech and personal. 

The slim filing, a summary of expected expert testimony, covers just three pages, one for each expert. The final authority Mr. Smith plans to summon possesses the “knowledge, skill, experience, training, and education beyond the ordinary lay person regarding the analysis of cellular phone data.” He is well versed in the “use of Twitter and other applications on cell phones.”

The expert’s mastery of the mobile could make him a linchpin of Mr. Smith’s efforts to persuade a jury that Mr. Trump’s actions on January 6 furthered an alleged criminal conspiracy to overturn the result of the last presidential election. The special counsel reports that the expert combed through data from a phone used by Mr. Trump as well as “one other individual.”

The expert has “determined the usage of these phones throughout the post-election period, including on and around January 6, 2021” as well as when Mr. Trump’s device “was unlocked and the Twitter application was open on January 6.” Also analyzed were “images found on the phones and websites visited.”

These secrets surfaced in software and could aid prosecutors in their efforts to pin blame on Mr. Trump for the chaos at the Capitol. Of particular interest could be a tweet sent from Mr. Trump’s account at 2:24 PM on January 6, where he ventured that “Mike Pence didn’t have the courage to do what should have been done to protect our Country and our Constitution.”

Seven hours and 37 minutes are missing from the official White House call logs for January 6, making those cell phone archives of paramount interest to Mr. Smith. Mr. Trump’s erstwhile national security adviser, John Bolton, tells the Washington Post and CBS News that he recalls “using the term ‘burner phones’ in several discussions and that Trump was aware of its meaning.”

In a statement issued in response to that report, Mr. Trump was quoted as saying that “I have no idea what a burner phone is, to the best of my knowledge I have never even heard the term.”   

Mr. Smith’s case rests to a not insignificant degree on proving that Mr. Trump leaned on Vice President Pence to act crosswise with the Constitution by refusing to certify the electoral results. Mr. Pence refused those entreaties, believing that such a refusal was not contemplated by the Framers, who wrote that the vice president “open all the Certificates , and the Votes shall then be counted.”

In order to access those phones, Mr. Smith needed to obtain a warrant. That required persuading a judge that there was probable cause that they contained evidence of illegality. The Supreme Court unanimously held, in Riley v. California, from 2014, that police are required to obtain a warrant before viewing the contents of a cell phone seized as incident to an arrest. The Fourth Amendment protects against “unreasonable searches and seizures.”

The data collected by this expert could explain how Mr. Smith has gained access to the innards of Mr. Trump’s X account, formerly known as Twitter. In a warrant for that trove, the special counsel requested the company turn over Mr. Trump’s direct messages, draft tweets and all engagement with, potentially, millions of users. The social media giant initially resisted furnishing that information before being compelled by a court order. 

While it appears that Mr. Smith could have a digital motherlode, the data from the phones could prove less than conclusive when challenged at trial. One of Mr. Trump’s aides, Dan Scavino, is believed to have composed most of the 45th president’s tweets, and could have held the phone during the time in question. That could undercut attributions of intent to Mr. Trump. 

Mr. Trump could also challenge the cellphone data on the basis of executive privilege. While his invocation of that doctrine has been met with judicial skepticism, messages sent from a president’s telephone would appear to be the sort of material that court’s could be inclined to shield from prosecutors.