Jinns don't transform into snakes! When they do they can't transform back! Old Jinns, who are fed up of their life, transform into snakes, to commit suicide. An easy way for Ahle Ilm to find that the snake that he killed is a snake or a Jinn, is to look at its blood. If the bleeds abnormally or/and its blood turns black in sunlight then its a jinn. If it turns whitish like, its a snake! Before killing a snake, it should be asked to leave 3 times, before killing it, if you have that time!