Peter Pitman, 46, was initially charged with murder after the body of his 75-year-old mother Janet Pitman was found in a field with a gunshot wound to the head.
Pitman, a farmworker, denied murder and was given a nine-month prison sentence suspended for two years after pleading guilty to aiding and abetting his mother's suicide in a mercy killing.
Bristol Crown Court heard how Mrs Pitman had endured 40 years of agony after being struck down with arthritis. She moved to live with her son at Charlton Mackrell, Somerset, 15 years ago but continued to suffer from the crippling disease. The court was told Mrs Pitman was determined to kill herself because of her poor quality of life and had been screaming with pain the night before her death.