OK I was talking about UK civil law.
It's easier for me to point out the Blackstone Bias in criminal law. However, the contemporary expert panel combined with the concept of binding arbitration would make better judgments in civil cases than legislators in 1886 who never heard the facts in the actual case.
If one considers criminal law, as you seem to want to do, the criterion quite rightly is proof beyond reasonable doubt, not just balance of probability. This is because a criminal record is a seriously damaging thing to saddle a person with for the rest of his life, and because the sentence may often deprive him of his liberty.
Requiring a two-thirds majority of the panel would achieve the same aim. This would avoid the vagueness of the reasonable doubt concept.
So even here, the most serious offences are felt to need the involvement of the public, in order to ensure justice is seen to be done by the people and not just by an elite who could be subject to state or other influence (bribery, inappropriate friendships, institutional "capture" by the police, etc.).
If you were falsely charged with a crime, would you want amateur jurors with an average IQ making the decision? A jury of experts, randomly selected by computer, would be my choice because I want them to make the right decision. If I was guilty, I'd opt for the kind of system you describe because I'm hoping it errs.
What it comes down to is that the exercise of the law has to be done in a way that the citizens can buy into as truly impartial. Your notion of expert panels would be immediately open to all sorts of challenge.
The panel members would first be tested on IQ. They would then be trained in a specialty and then randomly selected by computer for a particular case. They would not be instructed by judges or under the influence of the prosecution as amateur jurors are in the current system.