In the dreams only. Definitely not in real life, although I have been sent there for a case once. That was enough.
Are you working with the actual perp then? Getting information from them can be the real challenge.
I have empathy, but when you are staring down at a body, you have to have an off switch. I almost threw up the first time, but I got used to it, and I just try to go into the analysis of the scene.