Of course, scientists write books all the time about their field of expertise. A Brief History of Time (Stephen Hawking), the Feynman Lectures on Physics, the Principia (Isaac Newton). One might say it is common, actually, as the entire point of being an academic is to publish their work for other people to read and understand. I certainly hope you understand that the publication of work from a leading expert in the field is not evidence that the content of the book is wrong. An expert wouldn't publish incorrect information for a minute personal gain, because that would completely destroy his reputation and his career. That would make literally no sense!
Now, there are situations where non-experts may write a book to "line his/her coffers" as you say, and to exploit a situation for their own personal benefit. With respect to this case, can you think of any examples of this, Vixen? Do you think doing such a thing may taint their perspective and bias his/her perspective a bit, Vixen?
Well, no kidding! He wasn't there when the evidence was collected, as that would have been impossible since he wasn't involved in the evidence collection! And there wasn't enough material for Stefanoni to repeat the LCN analysis of the knife more than once, as required by international protocol to insure reliability (so innocent people don't get convicted on misleading evidence), remember? So how is Gill supposed to "see" evidence first hand that was either used up, destroyed by Stefanoni (remember how she destroyed the bra clasp by storing it incorrectly?), or collected 7 years ago?
Regardless, it is normal to write an analysis of evidence that you don't "see first hand". That you think this is unusual is one of the more ridiculous things you have said. It literally happens all the time in science. This is why scientists document their work. It's kind of the entire point of what they do; perform experiments and those experiments are reviewed by other people. This is how the entire scientific process works.
Well, he's actually quite literally one of the very top people in forensic genetics, and one of the founding fathers of the entire field. But I guess since he doesn't agree with you that makes him a disgrace.
Out of curiosity: if the fact that one of the very top scientific experts in their field publishes a factual analysis proving the DNA evidence against Amanda and Raffaele was unreliable and misleading does not convince you, what will? You literally cannot get a stronger refutation than that, short of gaining an expertise in molecular biology and looking at the evidence yourself (hint: everyone that has an expertise in molecular biology and has looked at the evidence themselves agrees with Gill). Instead, rather than incorporating this information and updating your belief appropriately, the world leading expert becomes a "disgrace" in your mind. Do you see a problem with this, Vixen? I ask again, if the opinion of the top expert in the field doesn't change your mind, and the opinion of every other expert in the field that has reviewed the case doesn't change your mind, and the laws of molecular genetics don't change your mind, what will?