A katana in the hands of a skilled martial artist can easily whack off a head or a limb. The few instances I've heard of body blows - say, a vertical whack down between neck and shoulder - the blade usually stops after maybe a foot of travel thru all those bones. I'm not sure if I've heard of torsos being whacked laterally apart, but I wouldn't be TOO surprised. Straight down on the head? I'm guessing it'd stop before it got as far as the sternum.
But I'm not convinced a butcher is a skilled martial artist. There are very specific ways to use a katana, and it ain't like a cleaver.