Sam is a doctor at Utara Medical Centre (UMC). UMC relies on his expertise to give medical opinions to the patients. UMC also relies on Sam's expertise to diagnose illnesses and diseases. He has full knowledge and vast experiences, therefore able to determine the conditions of patients who need to undergo surgery.

Looking at the nature of his work, give your opinion about Sam's status whether he is a workman of UMC or an independent contractor and suggest the appropriate test to be applied. Support your answer with a case.