Principle of Double Effect in action. It was not murder:
a) the death of the twin was not intended; the procedure would have been performed even if the twin would have survived.
b) the good of the procedure, a life, is at least equal to the evil, a death.
c) the procedure was a medical necessity for the health and survival of the surviving child, and there were no “safer” alternatives.
d) there was nothing inherently wrong with the procedure; seperation of conjoined twins is not in itself an evil.
In essence, the deformed twin was a “parasite” in the sense that it drained nutrients from the fully developed child without returning any of its own. Furthermore, such a deformed child was unlikely to survive for long, meaning that the life of the fully developed child would be in extreme jeopardy if left attached. A seperation had to be done, and would have been done under any circumstances. Nobody intended that deformed twin would die, but it was recognized as the definite, and unfortunate, outcome of the medically necessary procedure.