Harvard Law School professor emeritus Alan Dershowitz said Saturday that congressional lawmakers are violating the U.S. Constitution in what he described as a “show trial” against former President Donald Trump. The House impeachment brief (pdf) alleges that Trump incited a mob to breach the U.S. Capitol on Jan. 6 while lawmakers were convened in a joint session to consider certification of electoral college votes. Trump’s legal team denies the allegation and argues in a memo (pdf) that the trial is unconstitutional because Trump is no longer president. The team also argues that Trump exercised his First Amendment rights in calling into question the results of the election. Dershowitz argued that an effective legal defense is based on challenging the constitutionality of the allegations against Trump. “The best arguments he can make, and he will make, are the constitutional ones, namely the Senate had no jurisdiction over a former president and …