The moment juries or judges go beyond their functions, and take upon themselves to lay down the law or find the facts, not according to the law as it is, but according to the law as they think it ought to be, then the certainty of the law is at an end; there is nothing to rely upon; we are left to the infinite variety and uncertainty of human opinion; to caprice which may at any moment influence the best of us, to feelings and prejudices, perhaps excellent in themselves, but which may distort or disturb our judgment, and distract our minds from the single simple operation of ascertaining whether the facts proved bring the case within the law as we are bound to take it.
1 Cababe & Ellis' Q. B. D. Rep. 134. - Reg. v. Ramsey (1883)