We know this also because we've SEEN it happen before. Scooter Libby was found GUILTY of obstruction of justice even though there was no finding that he had engaged in the crime he was attempting to cover up.
Akerman writes in the New York Daily News:
"Barr’s statement is also legally wrong that corrupt intent can only be inferred if there is “first” a “finding that the President had engaged in the wrongdoing he was allegedly trying to cover up.” If Trump had simply been trying to have the Russian investigation dropped to avoid the political ramifications of having a criminal investigation pending against his campaign, that would be sufficient corrupt intent. There is no legal requirement of proof of an underlying crime that the obstructer is trying to cover up."
https://tinyurl.com/y2kmfhhk
https://www.nydailynews.com/opinion/ny-oped-what-bill-barr-doesnt-understand-about-obstruction-of-justice-20190115-story.html
