Former British SAS officer Simon Mann has been found guilty in Zimbabwe of attempting to buy weapons.
Mann said the weapons were to guard a DRC mine
Some 66 other suspected mercenaries arrested with Mann in Harare in March were acquitted of links to a suspected coup plot in Equatorial Guinea.
Mann had admitted trying to procure dangerous weapons, saying they were to guard a diamond mine in DR Congo.
But he denied a second charge of purchasing the weapons, insisting that the deal never went through.
Magistrate Mishrod Guvamombe said prosecutors failed to prove their case against 64 men arrested when their plane landed at Harare International Airport on 7 March
and two others already in Zimbabwe at the time.
The 64 men aboard the plane and three crew members have pleaded guilty to immigration and aviation violations carrying a maximum penalty of two years in jail and a fine.
The two others not aboard the plane are due to be freed.
The magistrate said he would begin handing down sentences on 10 September.
Fourteen suspected foreign mercenaries are on trial in the Equatorial Guinean capital, Malabo, for the alleged coup plot.
The verdict in that trial is expected in the middle of next week.
The government of Equatorial Guinea is meanwhile seeking the extradition from South Africa of Sir Mark Thatcher, son of former UK Prime Minister Margaret Thatcher.
He is currently on bail, facing charges of involvement in financing the coup plot - charges which he denies.
Lucie Bourthoumieu, a lawyer for the government of Equatorial Guinea, which still imposes the death penalty for serious crimes, said the country had "strong hopes" of Mr Thatcher being extradited.
"South Africa is co-operating, and they are willing to fight furiously against all mercenaryism and terrorism," said the lawyer.
The South African government says it has not yet received a formal extradition request but Equatorial Guinea has asked to interview Mr Thatcher.
There is no extradition treaty between the two countries and South Africa has policy of not extraditing suspects to countries with capital punishment.
The editor of news magazine Africa Confidential, Patrick Smith, described the judicial system in Equatorial Guinea as "ad hoc".
He told the BBC "there would be a lot of restrictions in extraditing someone of Mr Thatcher's stature".