Poisoning is an alternative way to commit manslaughter without committing battery (assault in Canada). Another way to commit manslaughter is by the equivalent of criminal negligence, which may not amount to battery.
When I was on a jury, they took a plea at the time that the two sides were about ready to sum up their cases.
You seem to know a lot about this 
.
Northern Piper is a Canadian lawyer. Also a violent felon (:D) but his knowledge mostly comes from his legal training.
To be convicted of battery, the defendant must have intended to commit the “harmful or offensive contact.” To be convicted of (involuntary) manslaughter, the defendant need only have intended to commit the act which led to the death.
A recent case that highlights just how strange these things can get sometimes: The Burned Boy. The facts of the case are very upsetting, so I’ll give you the short version:
Robbie Middleton, at age 8, was tied to a tree and set on fire. He survived, but needed extensive surgery, including skin grafts from the only unburned area of his body, which I believe was the small of his back. Unfortunately, due to the grafting he developed a rare form of skin cancer, and the skin cancer led to his death, thirteen years later.
His attacker was tried for capital murder. The prosecution argued that the skin cancer developed as a direct result of the burns he suffered years previously. He was convicted and sentenced to 40 years in prison.
I’ve obviously said too much. :smack:
From what I can figure out from the article, the offender was never actually criminally tried for the actual act before Robbie died. Thus, it doesn’t answer the double jeopardy situation question. If someone were convicted of whatever the charge is for seriously injuring someone by dousing them in gasoline and setting them on fire, would manslaughter 15 years later be double jeopardy?
(Plus, from what I understand of Canadian law - if this had been a Canadian case, the fact that the defendant was 13 at the time of the offense would mean he would only be tried as a juvenile, even over a decade afterwards, and faced a maximum of something like 3 years.)
The sentence for a young person convicted of first degree murder in Canada is a maximum of ten years. See Youth Criminal Justice Act, s 42(1)(q).