Double boarding is different, there is more overlap. And they really generally don't do two distinct jobs, simultaneously. I suspect your view of what constitutes a "decent lawyer" and the views of many other lawyers differ. I can assure you that a lot of this guys peers spend a lot more of their time keeping abreast of the law and servicing their clients than this part timer, and you are kidding yourself if you don't think someone dabbling isn't doing his clients and patients a disservice. Most of the time the peers of lawyers hauled up in front of the grievance commission or disbarred had peers and references who thought they were "decent" too.
Well, as someone who serves as a disciplinary hearing panelist, and represents lawyers in malpractice cases, I think I have an above-average ability to judge good lawyering. Almost without exception, the people "hauled up in front of" my hearing panels have bigger problems than keeping up with their reading, I can tell you that. The MD/JD I worked with did a better job trying the case I worked with him on than a lot of the "full-time" lawyers I worked with on other appeals.
Now, was he a good doctor? Hell if I know--never saw him at work in the ED. Maybe he's a great lawyer and a terrible doctor. Or maybe he doesn't have much of a life outside of work and is content to devote himself to what needs to be done to keep up with both fields. Or maybe he's a genius with a photographic memory. But the world is full of people who manage to do "what can't be done" on a fairly regular basis. I agree with you that most people aren't capable of pulling it off for the reasons you mention. But I disagree that it "can't ever" be done. This is the nontraditional medical student forum--how many times do you think someone has said "it can't be done" about what we're all trying to do here? Hell, I heard it as a somewhat nontraditional law student.
And this again is from someone who has had a foot in both professions and has a pretty good idea of what needs to be done. In either field if you are conscientious, you should often feel guilty not having read/done/practiced X enough, and that's if you are only doing one or the other field. Trying to do both means you do a lousy job in both, or you give one a very half *****Ed effort. I don't see other alternatives because the expectations of each full time career encompass the bulk of every day.
I've had much more than a foot in the legal profession, and a fair number of objective indicators that I'm very good at what I do, and I don't feel too guilty about not being able to keep up. Granted, I'm an appellate lawyer, so knowing the law is one of the primary things I'm expected to do--I spend most days researching and writing about the law, and I don't get distracted by having to deal with stuff like depositions, settlement conferences, and stuff like that. I can very easily see what a struggle it would be if I did, though. And that's not to say that I don't spend plenty of time having different feelings of career-related guilt. Not knowing the law well enough, however, isn't one of them. Since "keeping up with the law" is my primary job, it's not very hard for me to accomplish it. If I had to squeeze it in between trials and depositions, though, I'd have a very different point of view.
Your point is very well taken, though--I wouldn't want to have to keep up with a medical specialty on top of what I do now. But could I? Maybe if I gave up having what passes for a "life," sure. Not sure it's worth it to me, though. But there are a lot of people who say that about me--they wouldn't want to do what it takes to be me, and probably, people say it about you now.
My point here is that not every lawyer, or every doctor, has the same experience. Not all lawyers are the same: trial litigators have a much different life than appellate litigators, both of whom have much different lives than transactional lawyers, who have different lives than in-house counsel, and so on. I know just enough about medicine to know it's similar. What it takes to be competent is pretty much the same throughout, but how hard it is to do it varies pretty greatly depending on a number of variables.
And one thing is probably true--even if you can be competent in both, I imagine it's close to impossible to *excel* at either field. I think if you want to be the best doctor, or best lawyer, ever, you'll want to pick one or the other and stick with it.
Me, I've just gotten tired of the legal profession, so I don't think I'm in any danger of trying to "dabble" in it if I manage to switch careers.