Four men have been found guilty of trying to murder Rwanda's former army chief, Gen Faustin Kayumba Nyamwasa, in South Africa in June 2010.
Another two suspects, including the alleged ringleader and the general's former driver, were acquitted.
The magistrate said the shooting of Gen Nyamwasa was politically motivated.
The general had gone to live in exile in South Africa several months earlier after falling out with his former ally, Rwandan President Paul Kagame.
Rwanda has denied involvement in the shooting.
The sentences will handed down on 10 September.
The BBC's Nomsa Maseko says Gen Nyamwasa, his wife and daughter were in court to hear the verdict in Kagiso near Krugersdorp, about 25km (15 miles) north-west of Johannesburg.
"The magistrate has correctly observed that the conspiracy to kill me was politically motivated," he said afterwards.
'Paid in cash'
Rwandan businessman, Pascal Kanyandekwe, alleged to have been the mastermind of the assassination, was cleared of attempting to bribe South African police as they tried to arrest him near Johannesburg's Oliver Tambo airport in July 2010.
The items found in his possession proved he knew about conspiracy to murder but there was insufficient evidence to convict him, Magistrate Stanley Mkhari said.
Gen Nyamwasa and his wife had been returning to their home in Johannesburg from a shopping trip on 19 June 2010 when the would-be assassins approached their car.
The magistrate said that prosecutors had failed to prove beyond reasonable doubt that their Rwandan driver Richard Bachisa was involved in the plot.
The judge said it was clear the four other accused had met on a number of occasions to discuss plans to kill Gen Nyamwasa and that they were paid in cash.
Magistrate Mkhari said the plot was politically motivated and emanated "from a certain group of people from Rwanda".
He said he was satisfied that Hemedi Dendengo Sefu, a Tanzanian national, was the gunman and that Amani Uriwane, a Rwandan, Hassann Mohammedi Nduli and Sady Abdou - both Tanzanians - were his accomplices.
'Lucky to be alive'
Gen Nyamwasa helped Mr Kagame come to power and was appointed army chief of staff in 1998.
They had both been in the Rwandan Patriotic Front (RPF) rebel movement which put a stop to the country's genocide in 1994 after some 800,000 ethnic Tutsis and moderate Hutus were killed.
Mr Kagame became president in 2000.
Faustin Kayumba Nyamwasa
- 1994: Helped bring Paul Kagame to power and end genocide
- 1998: Appointed army chief of staff
- 2006: French judge accuses him of shooting down plane of Rwanda's ex-President Habyarimana in 1994, which sparked the genocide
- 2008: Spain accuses him of links to death of Spanish nuns
- Feb 2010: Leaves post as ambassador to India, flees to South Africa
- Accused of links to grenade attacks in Kigali
- June 2010: Shot and wounded in Johannesburg
- January 2011: Sentenced in absentia to 24 years by a military court
But their relationship soured and he was accused of undermining President Kagame, who some critics say runs a repressive regime.
Gen Nyamwasa said on Friday that he felt "lucky to be alive" - a second assassination attempt on him was foiled in 2011.
But he said his friend, Col Patrick Karegeya, a fellow exile and Rwanda's former intelligence chief, was not so fortunate.
The pair were convicted in absentia of threatening state security and went on to found the opposition Rwanda National Congress party.
Col Karegeya was strangled in mysterious circumstances in a hotel room in Johannesburg in January - no-one has yet been charged with his murder.
Rwanda's high commissioner to South Africa has denied allegations that government agents were involved.
"The orders to kill me came from the highest office in Rwanda," Gen Nyamwasa said.
"I am not the only person whom Kagame finds as a threat. Many people from my home country had also fled to South Africa, just like me," he said.
"Every regime should be tolerant to its own people and to the opposition. I'm targeted because I'm able to talk. Talking to the press is a serious crime in Rwanda."
The Rwandan government has consistently denied trying to kill its opponents.