Ex-cop could get eight years in prison for role in storming U.S. Capitol
A former Virginia police sergeant who joined Donald Trump's supporters
Robertson's defense attorney is asking for a sentence of no more than 15 months
Prosecutors said Robertson later destroyed the cell phones they had been using that day.
Prosecutors said Robertson "anticipated violence" on Jan.
He drank to cope with stress, he said, and fell deep into the "rabbit holes of election conspiracy theories."