Michelle Hunter, the step-mother of William "Billy" Hunter Jr., is being charged with aggravated assault, endangering the welfare of children and other related offenses on the four-year-old in 2011.
Several family members, including Billy's adopted sister, attended the beginning of the trial.
Items entered into court as evidence included a video of Chambersburg Detective Scott Mummert interviewing Hunter.
The trial is expected to continue throughout the next several days.
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