Having Juries decide criminal cases = 
Getting a group of 12 people to pass judgement on laws they know nothing about,without any bias etc is never going to work. Not now not ever.
From personal experience as a Juror,stories from others who have been jurors, and seeing things like this happen.
Actual calls from aJuror rooms:
"well the police probably planted that evidence there"
"I dont trust her (the victim) she seems like a slut"
"I'm going to vote not guilty just to piss you off"
"It was probably an inside job from the dodgy bloody [insert ethnicity]"
"he/she may not have done this crime,but he/she has certainly done something else wrong"
"I'm voting not guilty,I couldn't vote guilty because he/she is wearing a mask in the footage,I'd need to see his/her face on camera before changing my mind" (ruling out 99% of guilty verdicts in all robberies)
There have been many more....
The judge tells them what the law is and how it is applied in practicial terms and then the Jurors apply the facts to the law. What gets appealed with regards points of law is the judges direction in summing up.
When I read that story though it did seem as though the Jury had pushed the statute in a certain direction