In legal terms, a standard of care is used as the benchmark against a doctor's actual work. For example, in a malpractice lawsuit, the doctor's lawyers would want to prove that the doctor's actions were aligned with the standard of care. The plaintiff's lawyers would want to show how a doctor violated the accepted standard of care and was therefore negligent.
Standards of care are developed in a number of ways: Sometimes they are simply developed over time, and in other cases, they are the result of clinical trial findings.
A standard of care in one community will not necessarily be the same standard in another. Further, one doctor's standard can vary from another doctor's.