Court was in brief session ... when a cop logged in for a virtual hearing, rocking business up top, and party down below ... leaving the judge absolutely shook. You gotta see the vid -- Detroit Police Officer Matthew Jackson logged in for a proceeding of Michigan's 36th District Court on Monday ... and thanks to a very unlucky camera placement, the whole courtroom got an eyeful of his "uniform" ... boxers included (thankfully). The courtroom gasped in unison... and Judge Sean Perkins blurted