To me, that table set up doesn't look like something an adult would do. This looks like a glass top table. How many women would place a glass and a bowl ON the glass? She would carefully place them on the place mat. I had a glass table back in those days and it was a pain to keep clean, you did not set dishes on it. You made sure to use the place mats.
Also, (this is just from vague memory) I think Burke said somewhere that he liked iced tea. Also that they used to make it in a glass using the microwave. The large serving spoon in the bowl--again, more like something a kid would do. A kid might do it because they didn't know any better or just "because they could" without their mother scolding them. Now that Burke has admitted that he was up in the middle of the night, it's seeming more possible to me that he fixed that snack--used a huge spoon either to be silly or rebellious or didn't know better, set food right onto the glass table (maybe he usually got scolded for that too but he was up ALONE at night this time).
His fingerprints are on the dishes because he set up the snack. Patsy's fingerprints are on the dishes just because she took them out of the dishwasher and put them away. Patsy, when interviewed later, does say that the set up looks strange. This time she seems to be telling the truth when she says she wouldn't use the large serving spoon and that the set up doesn't look right. I don't think she had anything to do with the snack. It was Burke--up to mischief in the middle of the night.
So I don't know who killed JBR; no one does. But I do think this table scene shows that Burke made himself a snack, that he was alone at that time. At that age, some kids would be up to mischief, acting like the king of the house, up all by himself, doing whatever he wanted to do. Angry and rebellious, at least that night. Probably feeling pretty proud of how he had everyone fooled while they were asleep. Making his own food, playing with his toys in the middle of the night--just the opposite of what his parents have told him to do. Patsy would have told him to go to bed and get a good night's sleep so he would be ready for the next day. (hmmm, sounds a little bit like the ransom note but I don't want to jump to conclusions.)