The obvious start is whether is soft top or hard top. Check any sealing surfaces there. Windshield inspect. Turn on water hose and spray at that side and have someone inside to see if can duplicate and locate source.
The Weather stripping at the upper back part of the door is usually the culprit looking at the door staight on is deceptive the seal looks like it's nice and firm agianst the door surrounds but if spray water just on that corner you will eventually notice water droplet on the insdie of the window
go to this website report your problem
File a complaint
any problems like
shaking when you drive on highway
leaks when it rains