A jury in Jamestown, California - a former Gold Rush town which formed the backdrop for the Gary Cooper movie High Noon - convicted Ellie Nesler of a lesser charge of voluntary manslaughter, leaving her facing a maximum prison term of 11 years.
She now faces a second phase in her trial, which will determine whether she was temporarily insane at the time of the killing. If the court decides in her favour, it could impose as light a sentence as six months in a mental institution.
When Ms Nesler, a 40-year-old single mother, slipped into the court and shot her son's alleged molester, using her sister's palm-sized, semi-automatic pistol, her crime triggered a surge of sympathy for her plight, both in northern California, and further afield.
Her victim, Daniel Driver, 35, who had a history of sex offences against children, was accused of sexually assaulting her six-year-old boy and three others at a Christian camp. According to her, Mr Driver had smirked at her when he was led into court for a preliminary hearing on 2 April. She also claimed that her little boy had been so terrified by Mr Driver, whom she said had threatened to kill him, that he spent the morning of the trial vomiting. Overwrought, she left the court and returned with the gun, shooting the handcuffed defendant in open court.
Several banks set up Ellie Nesler defence funds, local shops put out collection jars, two country and western songs were written about her, and Hollywood agents descended in droves. T-shirts and car bumper stickers were printed bearing the legend: 'Nice Shooting, Ellie', as her supporters sought to portray her as a Wild West vigilante, forced to take the law into her own hands in the face of a lenient judicial system and run-away crime.
Letters of support poured in from as far away as Italy, and Denmark, although her fans began to dwindle after it was revealed that she was under the influence of methamphetamines at the time of the shooting, .
When the verdict was returned, Ms Nesler, a California gold miner's daughter who is reputed to be intensely religious, emerged beaming. 'I am happy and very hopeful,' she told reporters.
The second phase of her trial begins on 7 September and is expected to last three weeks.