How do you discover Truth? It depends. A lot. You have the
  well-known Scientific Method where you can test and retest and
  ask the same question as much as you like. But then - you have
  Law. Discovering Truth in the Legal System is a much different
  affair and depends entirely on where you find yourself.
  Trial-by-Jury is a part of Common Law and can be found in many
  countries. There are many exceptions, of course. But there's an
  interesting thing about Double-Jeopardy that we hardly ever
  think about: If you are found Guilty, you can typically appeal
  due to new evidence, faulty trial, any number of reasons. But if
  you are Acquitted (cleared of wrongdoing), that's pretty much
  it. Free to go. The burden of Guilt rests with the prosecution.
  It has many positive aspects; Imagine if there was no
  double-jeopardy rules: if you were unpopular for some reason or
  a theoretically corrupt system could retry you over and over
  again for the same crime, picking different jurors, changing
  parameters until you get the result you're looking for.
  [somewhat like the Scientific Method in fact] If we were dealing
  with chemicals or surveys, hypothesize, test, etc would be quite
  fine. But you're dealing with people. Messy, awkward, people
  with feelings and lives and things they gotta do each day.
  But at the same time, we have a rush of new methods of Science -
  especially in the cognitive science and DNA departments, among
  many other sciences. And, in an even more compelling manner than
  the woman who gets off from killing her kids then brags 20 years
  later and goes, "hah, YOU CAN'T GET ME NOW - should've done your
  job right back then!" - the new scientific methods are changing
  the 800 year old Common Law Double Jeopardy in significant ways,
  all across the countries that practice their versions of Common
  Law. The changes in the kinds of compelling evidence are quite
  interesting; although often too much Faith can be placed in
  brain scans and DNA tests, as we've seen... yet it does seem to
  be extraordinarily more helpful than "he said / she said / look,
  there was a cigarette butt at the scene of the crime that
  matched her lipstick and was her brand". Fine for its day, but
  our truth discovery processes are improving. Scotland and
  Australia almost seem to have an inverted Double-Jeopardy now,
  where Double-Jeopardy is basically allowed, except in minor
  crimes. I'm neither for or against any of this; I'm not nearly
  smart enough to know "what's right". But the differences between
  countries are interesting to me; and I think the Scientific
  Method is, indeed, finding its way into Court Systems, bit by
  bit, around the world in a way. The future should prove
  interesting. Will we ever have a computer replace a Jury?
  Perhaps. I expect we'd start seeing a panel of Scientific
  Experts entirely replacing the Jury System first. A piece of me
  still likes the "jury by peers" idea though; even with all of
  its problems. Are communities responsible for their own members?