The law doesn't already require that?
Unless there's a state that does based on their written laws, as far as I know, no.
From my own experience, the overwhelming majority of disability evaluations are done by the treating doctor, and unfortunately, the overwhelming majority of these reports, I do not trust.
These doctors do not have forensic training and may not even understand the legal definitions of disability. They may, for example, in a desire to help their patient, or in a less-than-honest/lazy move (so they won't have to deal with an angry patient), just write a report favoring disability.
The few times I've seen a "real" forensic evaluation is when an insurance company is put in a situation where they have to pay big bucks to someone allegedly harmed during work. The insurance company, not wanting to pay the big bucks, hires a forensic doctor to give a "real" evaluation.
For these reasons, I have found disability evaluations extremely frustrating when it's my own patient asking me to write an evaluation. I've started a policy that anytime I write a report on disability, especially if it's an outpatient, that I pretty much state that I can only go on the patient's own reported symptoms. Unless it's schizophrenia, schizoaffective disorder, dementia, or a disorder where the objective symptoms I can clearly see in the office to the point where I can tell it will affect their ability to work in a job that does not require much cognition, (e.g. a bagger in a grocery store), I'll pretty much write that I can only see the person's symptoms based on what they're telling me, and in evaluations like this, the risk of malingering, while not the majority, is still significant.
Even in inpatient, in a short term care facility. I'm not so willing to write a report for disability. In most of those cases, the patient improves dramatically in a few days. It's hard to tell if they can work or not. In these cases, I'd definitely recommend an occupational therapy assessment before the patient is discharged for added insight.
From there on it's really up to the judge. Insurance companies and government care will not reimburse doctors most of the time to write disability evaluations, so unless the Court orders me to do a "real" evaluation, (for which they're going to have to pay for it), or they order it upon a neutral doctor (which is what I recommend in the letter), there pretty much will be no evaluation by such a doctor.
And unfortunately, most judges I've seen don't understand this. They think we doctors are more capable than we are. Just like IM doctors often consult us for reasons that are ridiculous (e.g. "We need to know if he's telling the truth or not.") judges I've seen don't understand either. I've had several conversations with judges asking them to change their order upon me which is clearly inappropriate, but the worse of 2 evils. (E.g. a judge ordered I write an insanity evaluation when the defendant didn't want to use an insanity defense. The judge wanted to push this defense on the patient which is in violation of the Sixth Amendment. The judge, being the legal expert, not me should've known that, but for some reason this judge couldn't tell. I'll remind the judge that there's such a thing called the Sixth Amendment defining that a defendant has the right to choose their defense, and it cannot be forced upon them by the judge. I've had this happen several times. )
