I'm in a BS/DO program going to do UG. Take a leave of absence, do an accelerated JD probably at the University of Kansas (2 year program). Grab my DO, do a residency in ophtho or ortho. Then I may do health law as an attorney doing chart reviews/malpractice defense.
Ophtho and Ortho are both surgical specialties. While I have a lot of respect for DOs and understand that many come to decide they would prefer a surgical specialty halfway through, I don't really understand why you would plan
to get a Doctor of Osteopathy with the goal of doing a residency in one of two of the most competitive specialties that don't really even use much (if any) of the uniquely osteopathic practice. Why are you not hoping to get an MD? Or, why would you chose 5 years of residency over 3 when you ultimately just want to practice law?
As for the question in the OP...
Here's my background: I've been working at a BigLaw firm for the past few years and will apply to law school for Fall 2011. My husband is a 4th year medical student.
Even though I haven't taken a science class since my junior year of high school, I know about the whole medical education part, and I am familiar with legal education because I spend a lot of time with lawyers. MS3 and MS4 are totally different from MS1 and MS2, so I don't think it would be a big deal to split them up. You would just need to take Step 1 before starting the law part and would need to brush up on the medical part before starting your medicine or pediatrics rotation. Obviously if you want to practice medicine, you will need to do your residency as well.
Now, is it worth it? I really doubt it. Assuming you start right out of college and do a 3 year residency, you will be 31 when you finish with your training. That's 6 years of accumulating student loan debt and 3 years of making ~$40k/year after college. And what will you have gained? Yeah, an MD/JD looks impressive because who's insane enough to get two professional degrees? But I don't really see much benefit from either side.
Now, if you wanted to practice law and you have an interest in science, a masters or PhD in a science field is very useful for IP attorneys because they deal with a lot of patents and technical science terms. But I don't really see much benefit in an MD/JD other than bragging rights.