Former federal prosecutor Glenn Kirschner was struck by the “unusual” rapidity and method with which Judge Juan Merchan built out a jury in former President Donald Trump’s criminal hush payment case in Manhattan — and in a newly released video, outlined what he believed it meant. “We are knee-deep in jury selection in that New York courtroom in which Donald Trump is being tried in the first of his four criminal cases,” he opened on his “Justice Matters” series. So far, a number of jurors have already been seated, despite Trump’s efforts to interrogate them heavily about their social media usag…