Yes and no. There are a few practical things to consider, including what you're good at, what makes money, what the professional qualifications are, and how many hours you have in a day. Here are some options I've seen:
1) Have a career, and a hobby that you're passionate about.
2) Have a job in one field, which makes you money, while building a career in another field, possibly switching after the second one starts to take off.
3) Find a way to blend the two into one career. (Learning about pathology and how to write crime procedurals is definitely a possibility.)
The important thing to consider is that some jobs/careers require a lot more training than others, and a lot more concrete commitment. Becoming a pathologist means going to college, medical school, and probably a residency. Forensic anthropology, as shown in Bones, means college, and a PhD. This is not something that you can do on weekends, and neither is film, if your path means going to Hollywood and learning how to film/write there.
It's not out of the question for you to be a pathologist by day, and a filmmaker by night, but I think what you might want to do is see the reality of what people really do in these jobs; TV is really bad at showing you the boring bits of a job. :D See if you can find a doctor, and ask if they know a pathologist you can talk to. E-mail a nearby college's film department, and see if they have anyone who can talk to you about what it takes.
And good luck! It's a great thing to be passionate about stuff. Even if it makes your decisions more difficult, at least you'll always be interesting to talk with. :)