Motive is vital in evaluating probabilities.  Assad has never had clear motives to use chemical weapons and he denies that his regime has used them in the civil war.  The killer rebs have massive motivation in terms of triggering western intervention to aid them in making it appear Assad used chemical weapons.  Now just out of cold blooded calculation, it was not in Assad's interest to order a chemical weapons attack.  Apparently, we have no independent proof that he did.  Some expert analysts say that the dispersal of the chemicals was far too restricted and narrow to have come from an aerial attack.  There are many special interests working here.  Powerful special interests.  You may be prepared to accept the media verdict, I am not.  So here I criticize Trump first for killing and second for killing without an responsible investigation.