Can you get DNA from skidmarks? Need an expert opinion here. Where's Doc Baden?
Yes. Mucoid secretions of the colon/rectum. As easily as from saliva.
I think you are going to wish you hadn't asked but the answer to your question is "sometimes."
As you probably know, a biological cell is needed for DNA typing and the body excretes thousands of cells from the walls of the intestines in fecal matter. The problem is separating these cells from the, er, contaminants and of course finding the human cells among all the other, er, material present.
I am sure a real expert could tell you more, but I stayed at the Aruba Holiday Inn Express last night and feel that qualifies me to give you a layman's POV on this matter.