Tough call on this one, since we do not know the mindset of the 16-year-old at the moment of the crime. The water was microwaved, so it is possible the teenager intended to get some water that was hot enough for the prank but not hot enough to burn the child. Again, I am certainly not justifying the stupid behavior, but there is a possibility that the perpetrator is remorseful and had no intention of causing harm. Also: consider that these burns could have been caused by water in the 120-130 °F range if the water was on the child's skin for enough time. The idiot teen might have conceivably stuck his finger in the water and thought it was not too hot (millisecond exposure) but on the sleeping child the exposure may have been 30 seconds to several minutes, meaning water that seemed "hot but not scalding" coming out of the microwave had enough time to cause extensive burns if left on the skin much longer. "Scalding" water does not equate to "boiling" water, and while this was an incredibly stupid "prank," I think we do not know enough about the teen's actions and thoughts when he hatched this dumb idea.
We should also factor in the vast range of wattages on microwaves, and I can see how the accused teen might have misjudged the power of a microwave to bring harm. Heck, I cannot even consistently cook instant oatmeal in a microwave on the first try: a little more or less water makes a huge difference in the finished product and cook time, and to get oatmeal the way I like it in the same microwave every morning can be as low as 33 seconds and as high as 50 seconds, since I never measure the water first.
As another example, we have a dog who was accidentally burned by spilled chicken soup, and the problem was exacerbated by the fact that the howling dog ran around for a bit before we could get to her and get some cold water on her. She had significant burns on her back, and had to go to the animal hospital for a few days, plus some longer term wound dressing at our vet. The soup was ready to serve the family, but 30 seconds or so on the dog's skin was enough to cause second and third degree burns. Yet humans could have put it on a spoon, blown on it briefly, and suffered no ill effects.
One more time for the reading-challenged trolls: the teen did something incredibly stupid and harmful, and should suffer the consequences for his decision-making. My point above was merely to suggest that there may have been extenuating circumstances to this case that were not covered in the story as presented so far. As for those who condemn the parents: let's not judge them for something that is the sole fault of the teen who carried out this action. Are you suggesting that they were somehow lax because they (GASP) let a 16-year-old near a microwave and a water tap? It is not as though they left a gallon of whiskey, some Quaaludes, and a loaded shotgun with the kids and said: "Have fun, boys!" In my own experience as a parent, teens and children can be amazingly impulsive, and my wife and I have seen our share of adolescent stupidity right under our noses. Luckily all of ours graduated high school, had at least some college, and avoided major stupidity of the form taken in this case.
Anyways, a sad story, and I agree with madjack that I am glad so many people are helping out. This moves me to make better use of some PayPal cash that is currently collecting dust.