If you submit autographs to PSA/DNA, you are wasting your money. Let's start with the company's name: PSA/DNA.
Do you think this company has some vault somewhere with DNA of Muhammad Ali, John F. Kennedy, Elvis Presley etc? Of course not. And even if they did, what does that have to do with evaluating the authenticity of their signatures? Is DNA somehow transmitted from a person's hand through a pen to the paper? No. Therefore, the company's name is designed to FOOL you.
Second, how possible is it to conclusively identify the authenticity of an autograph that you never saw being signed? In some cases, it's easy, but in most cases, it's near impossible. It's like arriving on the scene of a car accident you didn't witness and declaring that you know exactly what happened and who's at fault. Unless you have video of the accident, you are piecing together circumstantial evidence and taking an educated guess.
Yet PSA/DNA thinks they have all the answers. They think they can determine the authenticity of everyone from Julius Caesar to Justin Bieber. They can't. They are scam artists and they know it. Unfortunately the rest of the world doesn't (at least not YET).