The US has a policy of no assassination of civilians. They do assassinate terrorist combatants and their senders since they participate in a "war". If the US did assassinate an Iranian scientist, this would have been a foolish departure from policy, because killing scientists is just too easy, especially scientists in democracies such as the US and Israel. I don't believe this has happened.
Mexico sentences five men to 697 years for killings of 11 women (AP)