There's no actual proof even the kavalactones killed them. The "slightly yellowish liquid" makes me think it was an extract, and there is no way of knowing what the extract contained considering alot of things are filtered through first pass metabolism, anything could've killed him. Heck, the cause of fatal allergic reactions are because of certain proteins making there way into the blood stream that are normally broken down first. When consumed traditionally, it's extremely hard to overdose on kava if even possible. Too much kava and you simply fall asleep from an overwhelming sleepiness.
