How the FBI can very easily hack the apple Iphone

Ok. I am going to make this quick plain and simple.  Even if they wiped their phone, the FBI can have a pretty good idea of what the password they used was. How? Good question. since most locations on a cell phone are random access what the FBI could do is take a laser and see where the most pressure points or finger smudge is located. That will then allow the FBI the ability to create an algorithm. If a phone has ten times the amount of oil residue of a certain amount of letters that when placed into a computer becomes a word. Well that is a good sign.  I am not going to give away the rest of my theory...but yeah.