Conducting an independent investigation into clandestine links between a presidential candidate and a foreign government sounds like a recipe for spending a lot of time digging through obscure documents, piecing together chains of emails, and tracking down nervous witnesses. But Special Counsel Robert Mueller has one source of information that was missing in similar investigations of the past—and it’s not exactly hidden.

President Donald Trump’s Twitter feed – packed with more than 35,000 time-stamped missives dating to 2009 – offers a treasure trove of evidence for Special Counsel Robert Mueller and his growing team of investigators, according to lawyers and veterans of past White House scandals.

It’s clear that Trump’s Twitter account offers an unending bounty of irony and hypocrisy for anyone who takes a moment to compare his statements of the past with his actions of today. There are no topics on which Trump hasn’t reversed himself, blatantly lied, or blamed President Obama. Often all three.

But what can it offer the official investigation?

... the @realdonaldtrump account gives investigators a detailed timeline of Trump’s thoughts and opinions – including where they might differ from official accounts – and can also be used to establish intent, which can be critical in a criminal investigation.

It’s hard to argue that your Muslim Ban isn’t a Muslim Ban if you’re laying out your desire to ban Muslims 140 characters at a time. And it’s hard to ignore Trump’s attempts to stop the investigation into Russian interference in the election when he’s served it up on a tray.  

Trump and Mueller are breaking new ground …

Legal experts couldn’t name a single example where a president’s social media posts have been cited in a federal criminal case. Twitter was in its early adoption stages when I. Lewis “Scooter” Libby, a top George W. Bush White House aide, was convicted in 2007 for perjury, false statements and obstruction of justice over his role in the investigation of who leaked the identity of CIA agent Valerie Plame Wilson.

President Obama did use social media, but darn it, Obama was scrupulously free of scandal and constantly aware that his posts on sites like Facebook or Twitter were being read by millions, meaning that his social media posting tended to be filled with dignity, statements that match his policies, and even … grammar.

Meanwhile, Trump hasn’t just provided a treasure trove of naked id on display, he’s proven to be a nightmare client for any lawyer.

Legal experts say the president’s recent statements, including his admission to NBC News’ Lester Holt that he had the Russia investigation in mind before firing Comey, as well as his comment reported by the New York Times that Comey was a publicity-seeking “nut job” helps them paint a poignant picture of the president’s intentions.

You don’t really have to work that hard to investigate Donald Trump. Just wait till he opens his mouth … or lifts a finger.