Failure to formulate a complete and detailed theory of the case, covering ALL FIVE steps of the sequential evaluation is the #1 reason that a Social Security disability claim may be lost at a hearing or court appeal, according to Atlanta disability attorney Charles Martin.
Mr. Martin wrote a very helpful set of practice tips, entitled Ten Common Reasons a Hearing or Court Appeal May Be Lost, that appeared in the January 2009 Social Security Forum. And I completely agree with his #1 reason.
You gotta have a theory of the case. If you can't articulate why each step of the sequential evaluation should lead to a finding of "disabled," you can't really expect the ALJ to reach a different conclusion at the hearing. The most important task for a disability lawyer is to develop a winning theory for the claim, and one reason to write a hearing memorandum is to test drive your theory of the case.
As Mr. Martin says, make sure your theory of the case covers all five steps of the sequential evaluation.