Complex sentence: William C. Rader is a former psychiatrist who administered injections of human fetal stem cells claiming their therapeutic value for a variety of illnesses, a treatment which is not allowed in the United States and which has no scientific validity.
Split into simpler sentences: William C. Rader is a former psychiatrist who administered injections of human fetal stem cells claiming their therapeutic value for a variety of illnesses. The treatment is not allowed in the United States and has no scientific validity.