So, absent any standards, the instructor's decision is a best guess that can be trumped by the prosecution's expert witness?
This is what I was trying to describe earlier, however the concept of "minimum standards" seems to elude some people. It can be summed-up like this:
1. Each diving location in the world may present the student/new diver with different hazards which may require a different knowledge base and skill-sets than another geographic location. What is reasonably required to be taught (and examined) will be dependent upon the local conditions where the diver is being trained.
2. All diver certification agencies specify a Standard that is required for certification.
Some certification agencies base their Standards on ideal conditions. The level of Student difficulty and course content of what is required by the agency varies from one agency to another.
3. Different certification agencies look at the Standards in a different way. One may require a student to successfully complete a "universal program" as the only criteria for certification. Others look at their Standards as only "minimum standards" and encourage their instructors to teach beyond the agency requirements. In no case should a diver be certified until s/he is adequately prepared for these conditions and the instructor has tested/evaluated the Client. In any case, the instructor (or LDS) presumably enters into a contract to prepare the Client to dive in the area specified. Payment is accepted and the diver is eventually certified to dive safely in the conditions specified.
4. If the instructor was found negligent, it would be determined in a criminal or civil court of law. In civil law (which may vary from jurisdiction) negligence usually is found when the instructor does not meet "the standard of care." This may be defined by what was "reasonable under the circumstances." As liability may be assessed by an act or omission (what the instructor did, or failed to do), Expert Witnesses would be usually called by both the Defense and Prosecution. The decision rests with the Bench.
5. If the Standards were felt to be insufficient, it would reasonably be held that the instructor should have either enhanced the training given (to prepare the Client for the conditions reasonably expected in the local area), or give a referral for the Client to be certified in more ideal conditions. Again the decision is dependent on the strength of argument and case law (as applicable) from both sides.
If the instructor involved can only provide a "best guess," I certainly wouldn't certify him as an Instructor to begin with. S/he should know what training is reasonable for a diver to be able to dive safely and train him accordingly. The instructor should actively teach/test and evaluate the Student and keep a written record.