AN Adelaide woman charged with murdering her husband by setting him alight says she just wanted to "purify his penis", to end an affair and have him stay with her.

Rajini Narayan, 46, has pleaded not guilty to killing 47-year-old Satish Narayan by pouring petrol on him and setting him on fire as he lay in bed at their Adelaide home in December, 2008.



Giving evidence in the South Australian Supreme Court today, she said that even though she suspected him of having an affair she still wanted him.



"He was my hero, the man of my life, the love of my life," she told the court.



"I was going to purify his penis, leave a mark there and he would remain with me. He would be mine."



But Mr Narayan died in hospital several weeks later with burns to 75 per cent of his body.



The accused said she had snapped, dousing her husband's back with petrol when he called her a "fat, dumb bitch".



She also told the court that she had been subjected to domestic violence for most of her 20-year marriage.



She said that sometimes it would occur once a week and at other times, twice a month.



"Sometimes it was just a slap, sometimes a slap and a punch and sometimes some kicking," Narayan said.



On one occasion in 1990, she went to see a doctor and contacted police after fearing she had suffered broken ribs.



But despite all the abuse, she said she desperately wanted her husband's love and felt his beatings were only to help her be a better person, to "idolise him".



The trial continues.