Manslaughter that results from negligence might be a homeowner that doesn't lock the gate to their pool, so a neighborhood kid jumps in it and drowns. I'm not sure, but I believe the homeowner can be charged with manslaughter (at the very least, they can be liable for damages; that much I know for sure, but I'm not sure if they can be held criminally liable), but in general, manslaughter is the result of intent, as in the case of lighting a bag of shit on someone's door step that results in a burnt down house and kills the woman inside.