Misty Stoddard was found guilty Friday of first-degree murder and aggravated child abuse in the death of her 11-year-old stepdaughter.
Jurors deliberated about three hours before returning the verdict.
"I am very happy that my daughter was seen as a person and not as this crazy kid," said Lisa Stoddard, the girl's biological mother.
The Sarasota mother took the stand in her own defense Thursday and stunned the court with revelations about her sex life.
Stoddard, 37, is guilty of killing Melissa Stoddard, her autistic stepdaughter, in 2012 by tying her to a wooden board and covering her mouth with duct tape, causing her to suffocate.
Stoddard said the board was purchased by her husband, Kenneth Stoddard, for sex acts.
"It was for bondage," Stoddard told jurors.
"So he wanted to tie you to the board during sexual intercourse and sexual relations?" asked the attorney.
"Yes," Stoddard said.
Stoddard also discussed the difficulties of having a special needs child. She said Melissa was violent, often attacking her siblings or family pets.
"She would wrap her arms around the dog or the cat's neck and squeeze them until the cat would start clawing at her," Stoddard said.
The mother of six also testified that Melissa threatened her newborn.
"As soon as you would look away she would bend the baby's fingers back until the baby cried," Stoddard said.
Her testimony directly contradicted the child's biological mother, who testified that Melissa was not violent.