The general thought in law is that you as a student shouldn't reall have your own opinion, so your research is to gather the opinions out there, and then your essay is structured to favour one or two particular arguments, weigh them against the opposites, and conclude that a particular viewpoint is best.
You probably covered this case in lectures or a seminar, so look at the recommended reading for that week, then use those sources to guide your research - often looking at footnotes and then going to look at those sources directly is a good method. It obviosly varies between Unis, but I normally use 20-25 sources for a 2500 word essay - about 15 of those will be articles and the rest books or possibly websites. You should aim to have an absolute minimum of 10, and as this is your first essay, make sure you keep track of your sources as you go along - record all the info you need for your citations, so that you don't need to trawl through sources for hours after you've written it!
As a general guide, no more than half your essay, preferably only a quarter to a third, should be explaining. The rest should all be argument. I'm not going to give you any substantive help, because that defeats the point of you writing the essay, but this is how I would break down the question:
To what extent, do you think it is justifiable to deviate (1) from fundamental principles (2) of criminal law by creating driving offence of strict liability (3), in the interest of maintaining road safety (4)?
I would address 2 first - outline the fundamental principles of criminal law. Then look at 3, strict liability offences in general - don't just look at driving offences, but all types of strict liability offence. Then look at 4, the specific case of driving offences and the reasoning - road safety. Here you would discuss the case - just a few sentences to explain the judgement, you don't need paragraphs explaining all of it. And finally, 1, is is justifiable? You should try to incorporate your overall argument throughout the essay, but dedicate a lot of words to your conclusion and your chosen (supporting) argument, don't just leave yourself 2 sentences at the end.
Remember to look at your mark scheme - law essays at my Uni are very different to anything I wrote at school. You don't just write A B A B A B therefore I think A. In my experience (it may be different for you, so check!) you have to write, the arguments are A and B, A is probably stronger. A > B, B > A, A > B, therefore A > B.