I have to keep reminding myself that not every item tested, directly relates to the case.
keeping it simple and logical, I'm thinking that the brown liquid is the spit from the Copenhagen chewing tobacco.
Here's a pic of the crystal light bottle and the tobacco from the trash.(the tin is to the right of the bottle)
I haven't been able to locate a list of its 2000+ chemicals, but will keep digging. But some of the chemicals listed in the docs are found in cigarettes, so are likely in the tobacco too.
Why is there no nicotine present if its from tobacco? Because the nicotine is absorbed in the tissue of the mouth when its chewed, and literally goes up in smoke when its smoked.
There don't appear to be any crystal light ingredients detected either. So not all chemicals/compounds/ingredients were tracable.
Now here are some google pics showing that spitting into a bottle is common with tobacco chewing, and looks similar to the crystal light bottle in the above pic.
It makes more sense to me that a bottle of icky brown spit was found in the same trash as the tobacco tin, than KC making a lethal cocktail and leaving it in the trash.
JMO of course.