First, everyone is assumed to be competent, not incompetent.  There's no such thing as
"evaluate for capacity to refuse treatment"-- there is only "evaluate for the lack of capacity to refuse."  The default condition is competent.  It is up to the clinician to show sufficient evidence to take away his right to make decisions; not up to clinician to determine if he can make decisions.  And in order to take away their rights, you have to have an exceptional reason.  Not a valid reason, an exceptional one.  Not "benefits outweigh risks" but "treatment is so urgently necessary that it justifies this gigantic suspension of his civil rights."

For example, if a patient is preposterously psychotic: eating feces, seeing aliens, channeling the Devil, and he has a temperature of 100 and you want to give him a Tylenol and he says no, can he refuse?  Can you force him to take it?  Absolutely he can refuse, no way can you  force it.  Even if he doesn't know what Tylenol is; even if he thinks it's a mind control pill from the CIA.  Because the relevant factor is the Tylenol-- it is not necessary-- not his psychosis, not matter how severe.

You can actually determine compentency without seeing the patient.  No lie.  Observe:

Surgeon asks if a patient is competent to refuse a necessary surgery.  Ok, when's the surgery?  "Next Thursday."  Consult over: competent.  If it can wait until next Thursday, it isn't urgently necessary, and it doesn't matter what his reasons for refusing are: you can't force someone to do something unnecessary right now.  On top of this, capacity evaluations are time sensitive; it's competency now, at this moment-- you can't judge whether they will or will not be incapacitated in the future.  Again, note that in this example, I didn't describe the patient's mental state; it isn't relevant.  What's relevant is the simple question: is there any overwhelming justification for me to force someone into this?  

Doctors have a very difficult time with this concept, so I'll give you an analogy: innocent until proven guilty.

So residents want very badly to tell me about the history, the symptoms, that the patient is depressed or delirious-- in more than half of their case presentations, they never even mention the required treatment ("it's a competency eval to refuse treatment")-- and their frustration with me is palpable ("wait, just let me tell you about his---") because I keep interrupting them to ask about the necessity of the treatment. 

I'll repeat: the treatment is the important thing, not the patient. Competency/capacity evaluations are situation specific.  There is no such thing as "incompetent to refuse treatment"-- there is only the specific case at hand: incompetent to refuse this one specific treatment in this one specific case at this one specific time."  Only judges are allowed to decide general imcompetence.  You're not a judge, are you?  Then shut up. 

And thus we come to the point: as clinicians trained in medicine's implicit system of parens patriae, they think they should be allowed to overrule the patient to do what's best for them.

And you say: well what's wrong with that?

First, what the doctor thinks is best is irrelevant.  We are talking about "substituted judgment" which means "what the patient would have wanted if he were competent."  This is not the "best interests" standard, in which doctors decide what's in the "patient's best interest."  The two might be different.   So again, the standard is not what the doctor thinks is right, but what the patient wants.  Period.  You don't like it?  Go back to Russia.

Second, is the  "slippery slope" argument.  If you're allowed to usurp a patient's rights to give them non-emergent treatment, where does it stop?  Can you force psychotics to stop drinking or smoking?  etc, etc.

Third is the reverse problem: if you are allowed to usurp their rights for non-emergent treatments, are you therefore obligated to do so?  Is it your job to chase them around and make sure they take their digoxin?  And if they don't-- then what?  Involuntary commitment?   Slip it in their drink?  Really?  If my wife dies of digoxin toxicity because the doctor gave it in her drink, but her other doctor was slipping her Lasix, who do I stab?

Fourth: what if the doctor is wrong?  Maybe the patient knows what's best for himself, given the context of his life?  I mean, it could happen, right?

And the fifth problem is political: if a clinician can determine what's best for patients-- even if its not emergent-- why can't the government?  Because they're not clinicians?  How about government doctors?  ("The U.S. Corps of Psychiatrists have decided all Democrats need Zyprexa."  Like that?)  It amazes me how obvious it is to many doctors that they should be allowed to do "what's necessary"-- forced antipsychotics, involuntary commitments, etc-- and these same doctors are apoplectic over Guantanamo.   Under what possible logic can we allow that a psychiatrist should be allowed to detain a patient against his will, for the safety of others, and not allow the government to do the same?  Oh, you think you are in a better position than the government to decide who is dangerous and who is not? Then look around you, ye mighty, and despair.

Let me explain to you the bind that you psychiatrists have put yourselves in.  If a guy says he's going to kill his girlfriend, then you're obligated to protect and/or warn: you hospitalize him, or call her, or both.  But if you decide he is not in any way under the influence of psychiatric illness, and you decide you should simply call the cops to let them handle it, you'll find they have absolutely no obligation to do anything because no crime has yet been committed.  Despite the fact that the side of the police car says "To Protect And Serve" they have no legal obligation to do either-- but, here's the kicker--you still do!  If he kills his girlfriend, you get sued, not the cops.  Think about this.

For the record, I'm not saying the government should have this power, I'm not saying Guantanamo is a good thing; I'm saying doctors shouldn't have the power either.

Before you argue with me, understand that I am not trying to be dogmatic, I understand the nuances of everyday practice.  But this is a power you do not want,  you should use it with reluctance and care, because every time you use it it hurts you, it chips away at the wall that stands between you and society, the wall that allows you to say, "look, I'm just a doctor, I just treat illness, I can't be responsible for people's behaviors."

----

P.S. It goes without saying, but I'm saying it-- if you do find someone lacks capacity to make a serious, urgent decision, for the love of God and all that is holy, don't then take it upon yourself to make the decisions for him.  Move to a surrogate decision maker-- spouse, kids, parents, relatives, etc; anyone but you!

P.P.S. Also remember that every time you determine a surrogate decision maker is needed, you are also responsible to evaluate that surrogate.  It has happened more than once that I suggest the husband as a surrogate decision maker only to find that he's even more whacked out than she is.  Don't laugh; you should cry.

P.P.P.S.  In Massachusetts, patients who are adjudicated  incompetent automatically get the court-- not doctors or family members-- as the surrogate decision maker.  Happy now?

P.P.P.P.S.  Controversy is heavy, but here are the things that, to my reading of the law, are not allowed to be done without court order: psychosurgery, forced sterilization, admission to psych hospital (but not medical), ECT, and antipsychotics.  There is sufficient case law to allow forced antipsychotics in cases of dangerousness or emergency ( Washington; Rogers;), but I'm not willing to concede much more than that.

P.P.P.P-- oh, come on: The Supreme Court has also opined about when it is ok to involuntarily medicate prisoners with antipsychotics: 1) Is it an important government interest? 2) Would antipsychotics further this interest?  3) Are the medications necessary to further this interest? (i.e. is there no other way?) 4) is the antipsychotic medically appropriate?  You will notice that without 1), you can't do it.  "Important government interests" are things that touch the Constitution, like right to a speedy trial.  This is a slightly different situation, but I thought you should know.