This question is for Doctors or anyone involved in forensics.?

It depends.

If there is any tissue or marrow left you could do a crude DNA analysis and look for X and Y chromosomes.

If you had some history you could do a bone size/mass analysis. We know that males and females have different growth curves and rates. Looking at the size of the bones, you could determine a number of factors if you started with at lest one bookmark point like date of birth.

If you look at a cross section of the bone, depending on preservation, there are celluar differences that will help determine this, as well as racial background.

One nice thing about fiction, is that you can take liberties. Look at the TV Show CSI. Its a hit. But do you really think it is all done that way? DNA analysis takes days not minutes. Most times, the CSi techs are specialized and do only one aspect, like fingerprint analysis, they do not disassemble cars, run simulaions and do fingerprint analysis. So the point is that iwth a good story, the little details are overlooked and forgiven. You could very easily fugde the science and few would notice and of those that did, if the story was decent few would care. Another example, Jurassic Park. It was based on science in concept. Cloning is possible. Amber contains insects with blood from the time of dinosaura. Why not combine the two and clone T-Rex. Sounds good, but it does not mention all the details that make this impossible. But it was a great story, so the reader just doen't even think about it.

Good luck with your novel.