Just a note on reverse onus provisions and when the legal burden is appropriate instead of merely an evidential burden: R v Chargot Ltd (t/a Contract Services)  UKHL 73 (10 December 2008).
Lord Hope, with whom the other Law Lords agreed, said at 28:
"Section 40 [of the Health and Safety at Work etc Act 1974] imposes a reverse burden of proof on the employer. In Sheldrake v Director of Public Prosecutions  UKHL 43;  1 AC 264, para 21 Lord Bingham of Cornhill said that the justifiability of any infringement of the presumption of any innocence cannot be resolved by any rule of thumb, but on examination of all the facts and circumstances of the particular provision as applied in the particular case. In para 30 he drew attention to the difference between the subject matter in R v Lambert  UKHL 37;  2 AC 545 on the one hand, where it was held that the imposition of a legal burden on the defendant undermined the presumption of innocence, and R v Johnstone  UKHL 28;  1 WLR 1736 on the other, where it was held that there were compelling reasons why there should be a legal burden. In the former case, where section 28 of the Misuse of Drugs Act 1971 was in issue, a defendant might be entirely ignorant of what he was carrying. In the latter, offences under section 92 of the Trade Marks Act 1994 are committed by dealers, traders and market operators who could reasonably be expected to exercise some care about the provenance of goods in which they deal. It seems to me that the situation in which the reverse burden imposed by section 40 arises is analogous to that in R v Johnstone. Sections 2 and 3 impose duties on employers who may reasonably be expected to accept the general principles on which those sections are based and to have the means of fulfilling that responsibility."
This direct – almost casual – approach to deciding the appropriate standard on reverse onus is refreshing in comparison to the intricate exercise that bills of rights seem to require, culminating in a balancing of rights to see if there is an infringement and, if there is, a determination of what limitations are justified in a free and democratic society.