The jury of eight women and four men returned their verdicts on Thursday night after a three-month trial in the SA District Court and more than two days of deliberations.
The independent member for Mount Gambier had pleaded not guilty to 20 counts of theft and six counts of dishonestly dealing with documents, allegedly committed between 2009 and 2013.
Bell was found guilty of 20 counts of theft, with 18 verdicts unanimous and two by majority. He sighed heavily in the courtroom when the first guilty verdict was read out.
The jury found him guilty of five counts of dishonestly dealing with documents, with aggravation of abusing a position of trust or authority found to be proven on each count.
Bell was found not guilty of one charge of dishonestly dealing with documents.
The trial was told of transfers between Bell's personal accounts and those of the not-for-profit. (Lechelle Earl/AAP PHOTOS)
The trial, which began in June, has heard evidence that Bell, 51, abused his position as an Education Department employee to steal more than $430,000 meant to help vulnerable high school students and used it to fund property investments and pay debts.
Much of the trial focused on the movement of money between bank accounts and included five days of evidence from a forensic accountant.
It was alleged Bell stole funds intended to support high school students at the Independent Learning Centre in Mount Gambier, to assist disengaged students who had returned to study.
During the trial, prosecutor Jemma Litster said there had been "backwards" transfers between Bell's personal accounts and the not-for-profits' accounts "but there was still $436,023 that went out that didn't come back".
Ms Litster said there was no doubt Bell was a man who was well liked by most people, with evidence that his personality and the way he interacted with people engendered trust and goodwill towards him.
"It's the prosecution case that he abused that trust and goodwill. That's one of the reasons why his fraud went unnoticed for so long," she said.
"It's just human nature. I suggest people are less likely to challenge or scrutinise the conduct of someone who they like or someone who they admire."
In his closing address, defence counsel Nicholas Healy said the prosecution case has "more holes than a Balfours crumpet" and described the prosecution case as "a trial by vibe".
"We are not characters in the iconic Australian film The Castle. The system (the prosecution alleges Bell used) is akin to 'the vibe'," he said.
Judge Rauf Soulio thanked the jury for being "very dedicated" to a "very difficult task that involved obvious sacrifice".
He exempted them from future jury service.
Bell was remanded to reappear for a directions hearing on October 15, ahead of a date being set for sentencing submissions.
He made no comment outside court.
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