The society has two funds which provide some compensation for theft by lawyers.
"The most annoying part of it is my mother and father who worked very, very hard and created the trust, my father stood in the queue with his sugar bag waiting for vegetables and a side of mutton during the depression," Mr Johnston said.
"They learned how to save their money and this clown just thinks it's his."
McKay stole $566,900 from family trust funds and estates without his clients' authority.
He converted trust funds from the McKay Hill Lawyers Trust Fund account for use that was not authorised.
McKay then asked the firm's account manager, Anne McAllister, to write false invoices, backdating them a year, which totalled more than $1 million just after he had been served with a notice of a trust funds compliance review. The firm folded within days.
The offending occurred between 2005 and 2010.
While giving evidence McKay claimed the account manager was "dipping her fingers in the till".
But, last week, Ms McAllister told the court she warned McKay of the position many times and anything she did was with his authority.
When asked if he was saying he never looked at the bank statements of his business, McKay said "there were other people to look after those matters".
Following the verdict yesterday, Judge Doherty said McKay had displayed a "flagrant abuse of trust" and that a prison term was inevitable.
Mr Jefferson told Judge Doherty his client was "a man of somewhat fragile health" who suffered spontaneous rib fractures. He also asked that his client be given time to put his affairs in order.
Crown prosecutor Chris Lange said the health issues could be addressed by Corrections.
The Judge said there were no reports to corroborate these health issues and McKay had had plenty of time to put his affairs in order.
Officer in charge of the investigation, Emmet Lynch had contacted witnesses, "who are also very relieved and pleased with the the outcome".
In September 2014, McKay was struck off the roll of barristers and solicitors, when he was found guilty on one charge of professional misconduct in acting for a number of parties in a series of transactions where there were strongly conflicting interests.
He had already voluntarily handed in his certificate and was suspended from practice.
The tribunal ordered McKay to contribute $70,000 to Standards Committee costs and reimburse the Law Society for hearing costs of $14,812.
A New Zealand Law Society spokesman said "it is always extremely disappointing when a lawyer is found to have committed theft from their clients".
"It is vital that clients are able to have the utmost trust in their legal advisers. When that is breached, the lawyer also lets down the whole legal profession."
McKay was remanded in custody for sentencing on April 6.
