Questions that this raises include:
- What sort of conduct can attract this liability: voluntary service at a citizens’ advice bureau, duty soliciting by barristers, pro bono services, preliminary advice which does not lead to engagement as counsel, advice concerning plea, applications for bail, discovery and other preparatory work, legal research, conduct of courtroom representation?
- Does a final decision by a court in the proceedings create an estoppel? To what extent would a collateral challenge to such a decision, as part of an action for negligence, amount to an abuse of process?
- What is the standard of conduct that amounts to negligence? Does it, for example, equate to professional misconduct?
- How should damages be assessed? If the client is guilty, does he have a duty to plead guilty at an early stage so as to mitigate any loss that might be suffered by endeavours (negligently conducted) to secure an acquittal?
- Can the barrister enter into a contract with the client to limit liability for negligence?
- Is this liability retrospective, and, if so, how far back does it extend?
The Supreme Court does not here seek to answer these questions, but rather recognises that developments in the law will be necessary as they are raised in particular cases.
Some indications of what may happen are given. In their joint judgment, Elias CJ, Gault and Keith JJ touched on issue estoppel, double jeopardy and abuse of process (paras 58-59), and concluded that it would be unwise to limit the potential use of the power to strike out proceedings to prevent an abuse of process (para 61). While a collateral challenge to a subsisting conviction may be an abuse of process, that will not always be so, and it is necessary to recognise that there may be exceptions (para 66). Tipping J disagreed on this point, to the extent of preferring a rule preventing collateral challenges to subsisting convictions (para 189), but Thomas J sided with the majority, citing his published views on the advantages of pragmatism over formalism (para 207).
Other matters for future consideration are mentioned in para 75:
" … Following the lifting of the immunity, it may well be necessary to consider whether reasons of legal policy impact upon liability for the negligent conduct of criminal proceedings. The extent to which the public interest requires redress to be obtained only or principally within the remedies provided by the criminal justice system itself will have to be considered. It will be necessary to consider too whether there are any limits to liability."
The standard of care was alluded to in para 78:
" … The application of liability "should not stifle advocates’ independence of mind and action in the manner in which they conduct litigation and advise their clients" [citing Moy v Pettman Smith  1 WLR 581, 599 per Lord Carswell]. Nor should the standard of care imposed be such as to force advocates into defensive lawyering which is contrary to the public interest in the fair and efficient operation of the criminal justice system. And establishing that negligence is causative of loss will not be easy in circumstances where the direct cause of loss is the imposition of an independent judgment."
Tipping J observed that an action for negligence could hardly succeed if an appeal against conviction had not succeeded (para 190):
"The decision of this Court in Sungsuwan v R  1 NZLR 730 makes it clear that the conduct of counsel, whether negligent or not, can afford grounds for setting aside a conviction if the Court of Appeal is of the view that there is a real risk that the verdict of the jury is unsafe. If that cannot be shown on appeal, counsel’s conduct could hardly later be found on the balance of probabilities to have led to an unsafe verdict. Real risk is a significantly lower standard to meet than more probable than not."
And he added, at para 200-201:
"The problems are likely to be more substantial in the criminal arena. Significant policy issues can be forecast. Should the law of torts award damages for negligence when the loss derives from a lawful period of imprisonment? Should the law impose on barristers a duty of care when other participants in the system, albeit for different reasons, owe no such duty or are immune from any liability for a breach?
"Contribution problems may be substantial. Seldom is a conviction likely to be set aside solely on the grounds of counsel’s negligence. The Judge may have had some responsibility to guard the accused against certain types of negligence by counsel. While some of these points, and no doubt others, could be invoked in favour of retaining barristers’ immunity, I consider they are better addressed as facets of legal policy in the context where they truly belong, rather than as support for a blanket immunity for barristers."
So, we enter upon interesting times. And, potentially lucrative ones for insurance companies.