The ABO blood system has been used to settle cases of disputed paternity. Suppose, as a geneticist, you must testify during a case in which the mother has type A blood, the child has type O blood, and the alleged father has type B blood. How would you respond to the following statements?

a. Man’s attorney: “The mother has type A blood, so the child’s type O blood must have come from the father. Because my client has type B blood, he could not be the father.”

b. Mother’s attorney: “Further tests prove this man is heterozygous, so he must be the father.”