Jurors deliberated more than two hours before finding Tina Marie Alberson, 44, guilty of second-degree felony injury to a child in the July 2011 death of Jonathan James. Alberson faces up to life in prison because of a previous felony conviction.
Testimony in the punishment phase of her trial began Friday afternoon.
Police thought Jonathan's death was heat-related until the medical examiner's report.
Alberson had testified in her own defense. She told jurors she limited Jonathan's water intake only a few times as punishment for misbehaving, and that she saw him drinking water when he wasn't in "time-out." She said she saw no sign that he was in medical distress.
The boy's fraternal twin brother, now 12, testified that Jonathan repeatedly asked for water and even pretended to use the bathroom in order to sneak a drink from the faucet before their stepmother ordered him out. Joseph James told jurors he was concerned for his brother's health but was too afraid of Alberson to do anything.
After her stepson died, Alberson was charged with first-degree felony injury to a child, in which someone knowingly or recklessly causes harm that creates a substantial risk of death. It carries a maximum penalty of life in prison.
The lesser charge for which she was convicted carries a maximum 20-year prison sentence, but jurors can sentence Alberson to a maximum of life in prison because she previously was convicted of aggravated assault with a deadly weapon.
During closing arguments Friday before the guilty verdict, prosecutor Carmen White described the case as cruel and unusual punishment, saying Alberson chose to deny her stepson "the basic necessities of life" instead of access to television or something else that he wanted.
The boy's father, Michael Ray James, 43, is set for trial next month.
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