Basically, the special is about the many ways that nature can give forensic scientist clues to solve murders. The special focuses on the life cycles of insects colonizing the body, the tendency of birds to collect hair from bodies to build their nests, aging a body based on the plants growing up through the bones, and more.
I found a couple preview videos on YouTube. If anyone finds better, please post them:
And here is the link to the Nature site: http://www.pbs.org/wnet/nature/crimescene/index.html