For some Social Security Disability hearings, a Medical Expert (ME) is scheduled to testify. This is very normal, but certainly not a frequent occurrence. In my own practice, I would estimate that I have had an ME in roughly 5% of my cases. These Medical Experts are similar to Vocational Experts in that they are scheduled by the Judge and paid by the Social Security Administration.
An ME will not be your doctor. An ME is an independent mental or physical physician who is expected to remain neutral. This doctor will review your medical records in the file and help the Judge understand what effects your impairments may have on you; though they often listen to your testimony, they generally only testify based on your medical records in the file. Judges often schedule Medical Experts for Social Security Disability cases that may deal with a little more complicated medical issues; also, in my experience, some judges schedule them often so they have a second opinion.
After claimant testimony, a judge will often ask the ME if the claimant meets a listing. If they do not meet a listing, an ME will often give the judge a description of how the individual will be limited, whether it be physical or mental.
Though an Administrative Law Judge is not required to follow an ME's opinion, it is usually a very convincing piece of evidence for them to follow. This can obviously be good or bad depending on what the ME says.
Social Security attorneys all have different experiences with Medical Experts, Judges, and how they interact together. If you have been scheduled one or more Medical Experts for your upcoming Disability hearing, be sure to ask your Disability attorney to give you a general idea of what to expect and the influence these doctors may have on your case.