Explain Holmes' statement that doctors make the greatest criminals. Why do you think he came to that conclusion?

In the statement, Holmes speaks to the doctor's profession as being an advantage to the criminal element. Doctors are familiar with different types of medications and poisons, what is traceable and not traceable, what call kill, and what can make someone very sick. Doctors are also experts in anatomy, precise in their planning and implementation of their plans. They are intelligent, generally well spoken, and more often than not.... patient.