Start with the first hypothesis: Israel poisoned Yasser Arafat with polonium. What would it take for that to be true? 1. Israel had, or could obtain, polonium. 2. Israel wanted Arafat dead badly enough to take a big risk. 3. Israel had the ability to poison Arafat with polonium. Each of these elements could then be researched—looking for evidence pro and con—to get a sense of how likely they are to be true, and therefore how likely the hypothesis is to be true.
Break each hypothesis down to its constituent elements - and then research how likely those elements are to be true
