close to the source of putin's personal wealth would have been by far the most dangerous things that he could do. >> reporter: in addition to a possible motive there was also the means. paul joyal says the fact that polonium was used to kill litvinenko leaves little doubt as to who authorized the murder. so does that mean it had to be putin? it could have been someone else with access to -- >> come on, come on, you're not going to engage in an act of nuclear terrorism in downtown london without the knowledge of the office of the president. >> today we begin the open hearings in the inquiry into the death of alexander litvinenko. >> reporter: in january 2015, a public inquiry opened in london. it's a victory for marina, who, along with her attorneys, fought not eight-year legal battle to make it happen. on the opening day, her attorney argued the evidence leads to one disturbing conclusion, which litvinenko himself reached before he died.