Can someone tell me how a "standard of care" deals with unique or novel circumstances?

Is it ever acceptable to deviate from a "standard of care"?
Is the answer to this question outcome dependent? (Hypothetically, when I was new to EMS, we had "Air splints" for stabilizing fractures. It turns out that they also applied a fair amount of pressure over a large area and could be used to apply pressure to large bleeding injuries. If it saved the patient's life; it's an innovative, field expedient, improvised procedure. If the patient died; could it be argued that it was a breech of the standard of care and grossly incompetent and negligent?)

If I failed to follow NFPA 921, but still came up with the "right" origin and cause, have I still violated the "standard of care"? If so, does that invalidate my finding?

Is it the methodology that is covered by the "standard of care" and not (necessarily) the opinion derived from the methodology - provided that it is consistent with the methodology?

Is there anything wrong with accepting Chapter 4 (Basic Methodology) of NFPA 921 as the "standard" methodology without accepting the rest of the document as a "standard"?