As it's impossible to identify and overcome all jury bias, there will be cases where the decision is arbitrary. If it weren't then appeals/retrials would not come to another decision.
The idea of innocent until proven is guilty is an ideal that isn't met in practice, some trials end up as a popularity contest.
If the jurors can ignore testimony and evidence on a whim then the system is still arbitrary.
But yeah, keep digging. How does it feel to not understand the point when it's right there in your face?
And even if you pick the perfect jury, then human nature slips in.
https://voxeu.org/article/path-dependency-jury-decision-making
Simple tabulations indicate that a defendant had a 10 percentage point higher chance of being convicted if their case followed a defendant who was convicted (69% conviction rate) versus one who was acquitted (59% conviction rate).
Based on that, a more formal regression analysis finds that the raw positive autocorrelation in the data is, in fact, causal in nature. This analysis studies within-jury decisions, and controls for all observable case characteristics (including more than 30 offence categories). A previous guilty verdict significantly increases the chance of a subsequent guilty verdict by between 6.7% and 14.1%. This positive autocorrelation is robust to multiple estimation strategies, independent of the extent of juror experience, and driven by the most recent cases as well as pairs of similar cases.