Just a brief intro - I am a senior lawyer at a very large criminal defence practise, and deal frequently with defending people accused of a wide variety of offences, and those who are having their civil liberties encroached upon via non-criminal proceedings such as ASBOs, Control Orders etc.

I am not an extreme liberal - I deal with some very unpleasant people who have committed serious crimes and deserve punishment, and indeed rehabilitation. Nonetheless I am dismayed daily at the erosion of our civil liberties by the flood of new legislation targeted at controlling public dissent and protest, and by the fact that the police are more frequently using existing laws (such as the Public Order Act) to unfairly target peaceful protesters and to criminalise those who wish to engage in civil disobedience.

In answer to your tweet "Any lawyers reading want to define the word 'serious' in section 14 1a here? http://s.coop/6tu (soon to apply to Parliament Square protests)", there is no precise definition.

Here's the section under discussion of the Public Order Act 1986:

14. Imposing conditions on public assemblies

(1) If the senior police officer, having regard to the time or place at which and the circumstances in which any public assembly is being held or is intended to be held, reasonably believes that:

(a)it may result in serious public disorder, serious damage to property or serious disruption to the life of the community, or

(b)the purpose of the persons organising it is the intimidation of others with a view to compelling them not to do an act they have a right to do, or to do an act they have a right not to do,

he may give directions imposing on the persons organising or taking part in the assembly such conditions as to the place at which the assembly may be (or continue to be) held, its maximum duration, or the maximum number of persons who may constitute it, as appear to him necessary to prevent such disorder, damage, disruption or intimidation.

As has sadly been the case for much of the legislation passed in the last decade the Public Order Act (although much older) is another example of legislation that is far too loosely worded.

The civil servants who draft legislation have become lazier over the years in using the words "reasonable", "serious", "appropriate" and other unquantifiable terms, when it would be safer for all concerned (judges, police, prosecutors, citizens) if they were more precisely defined.

The old saying that "ignorance of the law is no defence" is and always will be true. If you don't know something is illegal and you do it - tough - you're still guilty. However with the huge recent increase in legislation (Blair's government alone brought in THREE THOUSAND new criminal offences - to put that into context, there were 4,000 offences in existence since statute legislation began in the 17th century up until 1997), and the poor wording of much legislation, how can any citizen be expected to know all of the things that are illegal? Indeed, even when they do acquaint themselves with the laws, how is someone not qualified and experienced in these matters to determine what is "reasonable" or "serious" if the statute doesn't specify?

Well - the simple answer is - the judges and the lawyers don't know either, so you have no chance at all.

I attend dozens of training courses each year and subscribe to daily legal (case law and statute) updaters via email and legal gazettes, and it is still impossible for me to be au fait with absolutely everything. More importantly I have to challenge cases on the courts week in, week out, where someone is alleged to have done something that the police say was not "reasonable" in the circumstances and the defendant feels it was "reasonable". So - the courts have to hear all the facts and decide on the merits of the case. You may get acquitted - you may get convicted.

Sadly the only way to firm up any definition of a word in legislation is by establishing case law. If a case has never been appealed to a higher court on a particular bit of legislation then there is no definition beyond the wording in the Act.

For example - when acting in self-defence you may only use "reasonable force". Many cases have resulted in defendants being convicted when they were arguing they used reasonable force, but the court found it was not reasonable. The appeal goes to the Crown Court, and beyond that the Court of Appeal (or House of Lords if appealed further). At that stage the judge/law lords give a decision which becomes legal precedent, i.e. if they say X was reasonable force then it is, and that case will be noted by lawyers and police for future reference as to what should or should not be prosecuted.

Sadly there appears to be no case law at all on this issue (s14 POA) because it has never (as far as I can tell based on my research) been appealed.

So... like many areas of legislation there needs to be a "test case". Unfortunately that will only occur in a situation where someone is prosecuted under the Public Order Act, and appeals on the basis that the police did not have grounds to implement section 14 as they did not have grounds to believe "serious" violence or damage would occur.

The self-defence example is not as bad as this because it is easy for an appeal case to happen and the phrase "reasonable" is interpreted by the court.

With the Public Order Act the police are given the discretion to decide what "serious" is - and this links back to my point about Blair's legislative tidal wave. The laws brought in during that period relied very heavily on things being made illegal if the police felt they was not "appropriate" or "reasonable" or there was a "serious risk" of X or Y happening.

The problem that raises is that the discretion passes from courts to cops. It is very very difficult as a defence lawyer, no matter how obviously barmy or wrong the decision of the officer who made the arrest, to satisfy a court that the officer did not use their discretion properly. The court will always give the benefit of the doubt to the officer on the basis that the officer is deemed to be skilled, experienced, fair, honest and more importantly was present at the scene and therefore in the best position to make the call.

The reality is that many officers have a very casual attitude to violence against suspects and civilians, and many have very little understanding of the laws they are supposed to be enforcing. In part it is not their fault as many are given inadequate training, but in part it often is their fault as a worrying percentage of officers are simply dishonest in what they tell the court. They may well be caught out under cross-examination if they are foolish enough to give evidence that is different from their colleagues, but there are many many cases where it is impossible to challenge their account, as they stick together and are almost always likely to be believed by courts.

I am not saying that in every case where officers give identical evidence they are lying. I sure many cases involve defendants lying and officers telling the truth, but when you get ten people at an incident they don't all recall things exactly the same way, and there are likely to be minor subtle differences in their account and phrasing of what happened. So - it arouses enormous suspicion to see ten absolutely identical statements, absolutely word for word the same on every page, all produced on a computer rather than handwritten and therefore clearly a case of one officer typing a statement and 9 others cutting and pasting it.

If officers are given more and more power to decide what is or isn't a criminal act (I could go on for pages about new legislation where this decision is entirely in their discretion, and new powers that have been created for them to issue fixed penalties and conditional cautions) then we move towards a society where police officers are the entirety of the judicial system for some cases. There is no jury deciding on whether the accused is guilty and no judge to decide on the appropriate sentence. The officer does it all.

I recall reading 2000AD comic as a boy and the Judge Dredd stories. Imagine that, I used to think, a frightening future dystopia in which cops have stun guns and decide whether you are guilty or not and decide on your punishment. What a scary but laughably unrealistic vision of the future.

It couldn't possibly happen in reality - could it?