In February, the blog of Derwent & Tamar Chambers in Tasmania (worth a follow) linked to a paper on case theory prepared by Justice Kenneth Martin from the WA Supreme Court as part of the ATC Advanced Trial Advocacy Course. It's well worth a read.
Case theory is a fairly recent concept in the history of advocacy, but good advocates have been doing it forever. For example, in 1895 Oscar Wilde sued the Marquess of Queensberry for libel. Lord Queensberry's barrister, Edward Carson, had assembled many facts necessary to defend the suit. Wilde portrayed Lord Queensberry as a brute beguiled by lies; Carson countered in his closing address to the jury, "Lord Queensberry, in dealing with Mr Oscar Wilde, has been influenced by one hope alone — that of saving his son." At the closing, Wilde sought to withdraw his suit so comprehensively had Carson rebutted Wilde's case, but Carson pushed for a verdict, and the jury returned a verdict of not guilty. Whatever your thoughts about the whole case, it was a demonstration of both detailed preparation and good case theory by Carson for the defendant.
But there still aren't a lot of freely available resources about case theory; what it is and how to develop it.
So, what is case theory? I like to think of it as, 'What happened, and why?'
If you can answer that, there's your case theory. A prosecution or plaintiff's case theory must put forward a positive explanation of what occurred, and why, consistent with the evidence in the case. A defence case theory might be one that completely contradicts the prosecution case theory — throwing up a stark choice for the tribunal of fact — or might be an alternative case theory that suggests doubt. (Or, the defence might not advance any case theory, and simply say to the prosecution or plaintiff, 'Prove it.') Case theory isn't just motive, though it will often incorporate a motive, or suggest a motive that logically follows from the case theory.
A good example provided by Lee Stuesser in An Introduction to Advocacy is from Plomp v The Queen (1963) 110 CLR 234 at 241 - 3, per Dixon CJ:
It was proved that Plomp had formed a liaison with another woman whom he had promised to marry, that he had represented himself as a widower and that he was continuing the liaison. In the circumstances, proved by apparently credible evidence, it was open to conclude that Plomp had the strongest reasons to be rid of his wife. It is unnecessary to traverse all the circumstances in detail...
In the present case it appears to me that if the jury weighed all the circumstances they might reasonably conclude that it would put an incredible strain on human experience if Plomp's evident desire to get rid of his wife at that particular juncture, presaged as it was by his talk and actions, were fulfilled by her completely fortuitous death although a good swimmer and in circumstances which ought not to have involved any danger to her.
Stuesser writes, 'In Plomp the prosecution's theory would be, "Mr Plomp found another woman. He wanted to get rid of his wife. He chose murder."'
Another example is the notorious case of DPP v Stonehouse  AC 55. Shortly before his disappearance, John Stonehouse took out life insurance policies totalling £125,000, and payable to his wife on his death. His wife was ignorant of his plans. From the headnote:
In 1974, John Thomson Stonehouse ("the accused") was a well-known public figure in this country. A Member of Parliament and a Privy Councillor, he had held a number of ministerial posts in the Government during the six years up to 1970. Thereafter he became active in business through a company. Export Promotion and Consultancy Services Ltd., which he controlled.
By the summer of 1974, his personal finances were in a disastrous state. He decided to fake his death by drowning and to start life afresh under a new identity with money dishonestly obtained and clandestinely transferred to his chosen country of refuge, Australia [where he was living with his mistress Sheila Buckley]. He carried out this plan, but was discovered living in Australia under his false identity some five weeks after his pretended death by drowning. He was extradited and stood his trial at the Old Bailey on an indictment charging him with 16 complete offences of dishonesty and forgery and five offences of attempting to obtain property by deception.
The case theory there would be: Stonehouse was going broke, and wanted money to start anew with his mistress. He faked his own death to defraud his insurers to get that money.
The benefit of a case theory is that it provides a sense of direction and purpose for the advocate. It guides questions. Justice Martin notes in his paper that when we have to think on our feet, and wonder, 'What question do I ask this witness?", the case theory will give us the answer.
Similarly, if your opponent makes unguarded or careless objections to the relevance of questions, that provides a legitimate opportunity explain our case theory in order to show the relevance. This is why silly objections on the grounds of relevance can be so damaging to your own case, and manna from heaven for your opponent.
So not only does the case theory need to be consistent with the admissible evidence — after all, it must have a proper foundation, and can't simply be made up like a script writer creates a screenplay — it also needs to be consistent with human knowledge and experience. Otherwise, the fact-finder will simply reject the case theory, probably with egging on from the opposition advocate. Both examples above demonstrate good case theories that meet these requirements.
If you want to read more about this essential aspect of advocacy, you can find some in the Australian Advocacy Institute's advocacy manual, and a more expansive treatment in chapter 1 of Lee Stuesser's An Introduction to Advocacy.