Earlier this year, paediatrician Sir Roy Meadow was struck off by the General Medical Council, who found that his conduct as an expert witness at Sally Clark's trial had been unacceptable. A key criticism was that Sir Roy had strayed into areas beyond his expertise when setting out a statistical case against Mrs Clark.
Other experts and would-be experts might have wondered whether being struck off was an appropriate response to not having stuck to the point.
But in Sir Roy's case there were doubtless policy considerations at work. When a defendant's liberty is at stake, it is essential that there is public confidence in the system, and the expert that the system chooses to rely on. The prosecution's job is not to get a conviction at all costs, and we all want our criminal courts to reach the right results.
In civil litigation, such questions of policy loom less large. But all courts expect experts to be independent, impartial and to assist them rather than one of the parties.
Putting oneself forward as an expert witness means stepping into a very public arena and facing exceptional scrutiny. Architects are used to public exposure, but there are notable differences between being criticised for your architecture and being criticised for your expert opinion.
Rather than a range of critics, there is one - the judge.
Judicial criticism of experts is not uncommon. Reputations can be compromised whether or not a professional body gets involved. The ARB did get involved over the expert evidence given by Michael Wilkey in Gareth Pearce's failed claim against Rem Koolhaas.
Pearce said his work had been copied in the design of the Kunsthal in Rotterdam. The ARB exonerated Mr Wilkey, after the judge asked them to consider his conduct. The judge had formed the view that Mr Wilkey's evidence was so biased and irrational that he had failed in his duty to the court, describing parts of his evidence about copying as 'comparing apples to Thursdays'.
It is not necessarily one piece of work that is being examined. Skeletons can be hauled out of closets and used in cross examination. In Cala Homes v Alfred McAlpine (1995), architect Francis Goodall was confronted with an article he had written some years earlier called 'The Expert Witness:
Partisan with a Conscience'.
Mr Goodall confirmed that he had applied the principles expounded in his article to his expert report in the case. In the article, as well as saying the legal process makes no pretence of determining the truth, he likened an expert to someone who works the three-card trick, using sleight of hand to deceive the eye of the innocent rustic.
Perhaps unsurprisingly, the judge took a dim view and said so in no uncertain terms.
There is concern in some quarters that the judiciary should be more cautious about criticising experts, given the extent of the damage that can be done to an expert's reputation. But that is the way it works. Anyone thinking about setting up as an expert and putting their head above the parapet should be ready for whatever gets thrown at them - be it apples, Thursdays, or worse.