The Serious Fraud Office says it faced a high bar trying to prosecute all those running the failed Dominion Finance, with only one of three men on trial being found guilty of theft.
Dominion Finance Group, and its finance firm subsidairies, Dominion Finance and North South Finance, collapsed in 2008 owing about $400 million to about 6000 investors.
At the Auckland High Court on Friday, former chief executive Paul Cropp was found guilty of four charges linked to related party lending of $13.6 million which breached the companies' trust deeds.
Former company director Robert Whale and another man, who has name suppression, were cleared of all charges.
SFO acting chief executive Simon McArley said the decision shows how difficult it is to prove they all deliberately intended to mislead investors.
"What it highlights for us is the very high standard of proof that we need to reach in these criminal cases to establish those issues around knowledge and intent, and whether or not an accused is guilty."