In this site, which is aimed at the decisions of leading appellate courts, I do not usually comment on trials. However, today our little nation is abuzz with discussion of the implications of what the media call the Waihopai spy base case.
Some people damaged some big plastic domes that cover secret communications facilities. I am vague on this description, but for me the most interesting thing about this case is the revelation that the big white domes can be slashed with a knife to expose the underlying things. Aerials and whatnot. The people were put on trial and yesterday were acquitted by a jury of offences like burglary and wilful damage.
What was their defence? That is not really the point. What matters is that a jury decided the case, and acquitted when a judge almost certainly would have convicted.
The case illustrates the role of juries in bringing community standards to the law. The common law's origin is the customs of the realm, and those customs were based on what people thought was reasonable. If the community thought that what a person believed and what he did were reasonable, then he would not be held to be acting illegally. You can apply the same criteria today to the criminal law. Although offences are now statutory, their definitions will always - except for some minor offences of absolute liability - be such as to permit acquittal of people who have held reasonable beliefs and who have acted reasonably in pursuit of those beliefs. Sometimes the law is more generous, allowing a defence if the belief was unreasonably held as long as it was honestly held (for example, self defence).
The best arbiter of what a community believes to be reasonable is a jury. This is recognised by courts (see the discussion by Heydon J in AK v Western Australia  HCA 8 at paras 90-98) and by law reform bodies (see the New Zealand Law Commission report "Juries in Criminal Trials" para 78). There are limits to the extent to which juries should be admired (as I have suggested). Even so, if you say the jury was wrong in this case, you have to show that community values are such that what the defendants did was, in the context of what they reasonably believed, unreasonable.