When I was trying to pick a profession for Trish Maguire, the detective character in the series that began with Creeping Ivy, I knew I didn't want her to be a police officer. There were too many police procedurals being written then, and I couldn't see any way to develop that particular sub-genre to make it my own. I also knew I didn't want to get bogged down in all the details of canteen culture, the Police and Criminal Evidence Act, custody sergeants, incident rooms, and car chases.  And so I made Trish a barrister, having no idea what a challenge I was setting myself.

At that stage, I knew very little about the workings of the English legal system. I even got in a muddle about civil and criminal trials, which are, of course, quite different. All I knew for certain was that I reverenced barristers for their brains and wit, their ability to master a whole new subject each time they receive a brief, their story-telling talent, and their sometimes mesmerising dramatic skills.

I learned more – a lot more – quite quickly. Lucky enough to have several friends at the Bar, I was able to ask for help each time I came up against something I didn't know.The trouble was remembering to check things I thought I did know.

If you're certain about something, such as the fact that human beings walk upright on two legs, you're unlikely to verify it. But your memory can let you down. I'd fallen into that trap in an early instalment of my previous series, when I'd taken a lot of trouble to find out, for example, exactly how much alcohol remand prisoners were allowed each week (that's no longer an issue because alcohol in prisons is now banned... I think) but I hadn't even considered checking my assertion that you can't get bail for murder.  Ooops. I looked a complete fool and was justly criticised both by the barrister who had given me most of the accurate legal facts in the novel and by Frances Fyfield in a review. A lawyer as well as a novelist, she is ideally placed to assess how well the rest of us do our work.

In her fiction she manages her legal knowledge with a light hand, but some of our other colleagues have said they have difficulty deciding just how much law to include in theirs and how much they can assume readers know. Another lawyer-novelist who has worked it out is Elizabeth Woodcraft. She told me her method:  ‘Sometimes you are just painting a background and can include a few phrases like “but remember the provisions of the '96 Act” or “the judge has released us until 2”, which make no difference to the story but add flavour. At other times you need to be more precise, because the plot may turn on it, and then it's like trying to create the atmosphere of a foreign country or language, you put in a word or expression, followed by the briefest of translations.’

Deciding exactly how brief to make that translation can be tough.  Give too much and you bog the story down;  not enough, and your plot will be incomprehensible to English readers, let alone those from countries with quite different legal systems.  If you dramatise the explanation by means of dialogue between one knowledgeable character and one naive one, you risk the kind of conversation that goes like this. Q:  ‘He used an Uzi, did he? What kind of gun is that?’  A:  ‘It's a sub-machine gun, you know.’  Which will always seem artificial.

The only other options are introspection – having your character musing ‘of all the sub-machine guns he'd ever heard of, the Uzi was the most useful for...’ - or a paragraph of straight-forward explanation. There are problems with all these methods and they have to be used sparingly if the novel isn't to read like a text book.

It's not always easy for text-book authors either. Once I'd realised how little I knew, I bought an excellent basic guide to civil law, (A Practical Guide to Civil Litigation, Hill, Wood & Fine) which includes the suggestion that, as a solicitor expecting clients for a meeting, you should send them ‘a map showing how to reach your office (if you are meeting there)...’  Wouldn't any solicitor be able to work out that s/he need not provide such a map if the meeting was to be elsewhere?

Unlike such conscientious guides to reality, novelists and script writers have to find ways of injecting drama into their work, and it can be difficult to do without stretching credulity. Anyone who has watched a trial, particularly in the civil courts, where Trish Maguire practises, will know that there are very few dramatic moments. This may well be why the television series Judge John Deed makes every practising lawyer I know wince.  

I love it. It's often funny, sometimes touching, and always watchable, but I'm told it doesn't give an accurate representation of English legal life. For one thing, television serials need to use the same characters in every episode. This means Deed is often sitting in court with his ex-wife appearing for the prosecution, their daughter as the junior on the other side, led by his current mistress. This doesn't happen in real life.

The necessary tension often comes from politicians leaning on Deed to arrive at judgements based on expediency rather than law. I'm sure real politicians are often tempted to do this, and it may indeed have happened occasionally, but it is certainly not as commonplace as it appears from the series.

In other kinds of fiction, novelists can get away with anything, provided they write convincingly.  But it seems to me that those of us who use the law as our background have a duty to make it as accurate as possible. Otherwise people may take our made-up stuff as fact.

It is easy to lose respect for any legal system. I recently read Linda Fairstein's latest novel, Death Dance.  As well as writing gripping legal crime novels, she was for many years leader of the Sex Crimes Unit of the District Attorney's Office in Manhattan and so she knows exactly what she's writing about.  In Death Dance she includes a judge who addresses the prosecution lawyer as 'missie' and 'hon' and is embarrassed to have to listen to details of the alleged rapist's crime. My respect for US justice definitely faltered as I read the scene.

No novelist can ever be perfectly accurate without sacrificing pace and tension, but I do believe we have to try to get it right and avoid making the legal system look foolish or dishonest when it is not.

Natasha Cooper’s novels featuring barrister Trish Maguire include Creeping Ivy, Keep Me Alive and Gagged and Bound.