Anthony Sannd was yesterday found guilty of stealing the Tissot masterpiece Still On Top from the Auckland Art Gallery.
A jury in the High Court at Auckland also found Sannd, aged 48, guilty of the armed robbery of an Amourguard security van and the Waiuku ASB.
He was further convicted on three charges of unlawful possession of a firearm and two charges of theft.
Sannd, who had been representing himself for much of the three-week trial, showed no emotion as the jury delivered its verdicts after more than five and a half hours.
He was remanded for sentencing on September 24.
Outside the court, the officer in charge of the case, Detective Sergeant Gary Lendrum, said it was a pleasing result.
The painting was crudely cut from its frame during an armed holdup by Sannd, also known as Ricardo Genovese, on August 9 last year. The thief escaped on a motorcycle.
He later demanded a $500,000 ransom for the safe return of the Tissot, which police found hidden under a bed at the home he rented in Waikaretu, south of Port Waikato, eight days after the gallery robbery.
Summing up, Justice Potter told the jury that the Crown's case was based around two stolen motorcycles used in all three of the armed robberies and found in Sannd's possession.
Sannd had denied owning many of the items found on his property by police linking him to the robberies, saying he did not put them there and did not know why they were there.