Mr Yettaw made two visits to Aung San Suu Kyi's house
John Yettaw is a 53-year-old American who was sentenced to seven years in prison but then deported after swimming to the lakeside home of detained Burmese pro-democracy leader Aung San Suu Kyi.
A Mormon, Mr Yettaw said he had been sent by God to deliver a warning that she would be assassinated.
Police fished him out of the lake after he had stayed uninvited at Ms Suu Kyi's home for two nights, sleeping on the floor.
At the time Burmese media reported that Mr Yettaw was carrying a large water bottle, presumably as a buoyancy aid, as well as a US passport, a torch, pliers, and US and local currency.
Images circulating on Burmese official websites apparently taken by Mr Yettaw himself showed a heavy-set middle-aged man. In one, he was shown wearing improvised flippers on his feet.
His detention led to that of Ms Suu Kyi, who was sentenced to an additional 18 months of house arrest over the incident - enough to prevent her from taking part in elections scheduled for 2010.
Mr Yettaw's seven-year sentence was to include four years of hard labour. But, on 15 August, the Burmese agreed to deport him, and he left with US Senator Jim Webb a day later.
The decision followed a meeting between Senator Webb and Burma's military ruler Than Shwe.
Soon after Mr Yettaw's arrest Ms Suu Kyi's lawyer said her supporters were "very angry with this wretched American", whom he called "a fool".
"He is the cause of all these problems," said the lawyer, Kyi Win.
US embassy staff have been able to meet Mr Yettaw briefly
Opponents of the government have said the bizarre circumstances were used as a pretext for keeping Ms Suu Kyi locked away.
Ms Suu Kyi's lawyer said Mr Yettaw had broken into her house once before, in November last year, and she had immediately sent him away.
On the second visit in May, he reportedly arrived at her house exhausted, lying down with cramps in his legs. Ms Suu Kyi's companions heard him groaning but did not let him in until after dawn.
In her closing statements Ms Suu Kyi said that in allowing Mr Yettaw to stay she had acted "without malice, simply... to ensure that no-one concerned should suffer any adverse consequences".
She even defended him, saying he had a right to say what he believed.
Shortly before the verdict Mr Yettaw was treated in hospital in the Burmese capital, Rangoon, after suffering from epileptic seizures.
A Vietnam veteran, from Falcon, Missouri, Mr Yettaw is also said to suffer from diabetes and heart trouble.
His ex-wife, Yvonne, told the Associated Press news agency that he had recently been working on a psychology paper about forgiveness after trauma, which took him to South East Asia.
John Yettaw used an improvised pair of flippers for his swim
Mr Yettaw's wife, Betty, described her husband as eccentric but peace-loving.
"He does not have a political agenda and meant her [Aung San Suu Kyi] absolutely no harm," she told AP.
Mr Yettaw has claimed to have had a traumatic childhood, and his wife said he suffered a head injury during military service that caused blackouts and seizures.
His 17-year-old son died in a motorcycle accident in 2007.
"After Clint's death, he took something that was already of intense interest to him because of previous experiences in his life, healing/forgiveness following traumatic events, and threw himself into his research, which precipitated his six months in Asia last year," his wife said.
Soon after his arrest, neighbours in Falcon gave a mixed account.
One, Mike Assell, told CNN: "He was just a very intelligent man to talk to, he was very literate, he had a good vocabulary and you could talk to him and he understood what you were talking about."
Other unnamed residents alleged that he struggled with drinking and post-traumatic stress disorder, CNN reported.
The Thailand-based independent Burmese publication Irrawaddy said Mr Yettaw appeared to be one of the many "self-appointed saviours" in Burma - foreign democracy activists using direct action to achieve political change in the country.
Among these is Briton Rachel Goldwyn, who in September 1999 was sentenced to seven years of hard labour for singing pro-democracy songs in Burma. She was released after two months.
Her detention came shortly after another Briton, James Mawdsley, was arrested for handing out anti-government leaflets. He was sentenced to 17 years in prison, serving just under a year.
Irrawaddy magazine criticised the "activists, experts, apologists, lobbyists, scholars, opportunists, do-or-die religious zealots and mercenaries" who have attempted to make a change in Burma on their own.
The "naive acts cause more harm than good", it said.