Charged with looking into aspects of the taxpayer system for funding defendants, she had nothing but bad news to deliver when the report was released late last week.
She found that lawyers and defendants were "abusing the system to the detriment of clients, the legal aid system, the courts and the taxpayer".
The justice system was being undermined by more than 200 corrupt lawyers who are rorting legal aid; some lawyers were taking backhanders and charging illegal "top-up" fees; every court was affected but Manukau District Court, in South Auckland, was the worst with up to 80% of its lawyers "gaming the system"; "car-boot lawyers" often met clients at court with no preparation; defendants were manipulating the system by engineering dismissal of lawyers to prolong proceedings; many lawyers simply did not turn up for cases, usually because they were double-booked.
The legal profession was working as a business not a profession, Dame Margaret said.
Good lawyers, she added, left criminal law not wanting to be tainted by association, creating "a race to the bottom".
The review, by any measure, is a stunning indictment of the legal profession.
Dame Margaret is one of the country's top public servants, a former head of the Department of Social Welfare, and is no stranger to conducting such reviews.
Her inquiry of police conduct following the Louise Nicholas furore was similarly hard-hitting, if not quite so unconstrained in its vocabulary.
So it must be held that, as dramatic as it is, her choice of language is deliberate and reflects the gravity of the situation as she sees it.
It is a clear call for urgent reform, which Justice Minister Simon Power has already initiated.
On Monday he announced that he had accepted the resignation of four members of the board of the Legal Services Agency (LSA), was reducing the membership of the board from six to four, and was beginning work on other recommendations in Dame Margaret's report, in particular "to fold the LSA into the Justice Ministry".
Integrity is critical to the credibility of the justice system.
At face value, that integrity has been seriously compromised by a "small but significant" proportion of lawyers.
Dame Margaret's report is a refreshing departure from the softly-softly, offend-nobody, mandarin-speak that often accompanies such reviews.
Those operating the legal aid system in a cavalier, or indeed illegal, fashion have been put on notice.
But if there is a note of disquiet surrounding the report, it is the extent to which it lacks hard evidence and documented cases of corruption and systematic abuse.
That 80% of the lawyers operating out of the Manukau District Court might be said to be corrupt - without corroborating evidence - at least raises the spectre of hyperbole attendant upon the report.
If it is true, it is a shocking scandal, and even if the percentage is a quarter of that, it is entirely unacceptable.
Such citations without names, cases and defendants, and based on anecdotal observation and hearsay evidence, would be summarily thrown out of the very courts that Dame Margaret has investigated.
It is, therefore, not entirely surprising that while her remarks have been met with concern, degrees of doubt have also been expressed by senior lawyers, including some from Otago.
Doubtless others around the country feel similarly.
Many honest lawyers doing their best to defend clients under what some claim is already an uneven economic playing field will be deeply aggrieved by the taint on their professional reputations.
Others may think that the move to disestablish the LSA, and take the task of funding legal aid into the Justice Ministry, has unwelcome political overtones.
That ministry funds the Crown Law Office, which oversees the prosecution "service" - at present undertaken by private firms under "warrants", an arrangement peculiar to New Zealand.
This system is about to be reviewed and should there be recommendations for a directorate of public prosecutions within the ministry and, effectively, a national public defence service as well, the scope for conflict and potential for political interference may escalate.
Be that as it may, Dame Margaret's report is deeply concerning.
The independent body which has existed to gauge and govern legal aid processes appears to have been found to be wanting, and doing nothing about it is no longer an option.
