Who is Geoffrey Berman, the powerful US attorney refusing to step down?

(CNN)Geoffrey Berman, the powerful US attorney for the Southern District of New York who has been thrust into the national spotlight for refusing to leave his post, has a long history at the prosecutors' office in New York and held a position on President Donald Trump's transition team before going on to investigate a number of Trump associates. Berman was an associate counsel in the Office of Independent Counsel during the Iran-Contra investigation, where he prosecuted a former CIA employee for tax fraud, before serving as an assistant US attorney in the Southern District of New York from 1990 to 1994. During his first run as a US attorney, he handled criminal prosecutions involving tax...