The victim was described only as an infant.
The incident took place in 2009, but authorities only recently became aware of it.
The San Bernardino County District Attorney's office has issued an arrest warrant, charging Santo with lewd acts with a child.
Santo is Hispanic, stands 5 feet 6 inches tall, weighs 150 pounds, and has black hair and brown eyes.
Anyone with information related to the case was asked to call Detective Tony King at the San Bernardino Police Department at (909) 388-4955, or the SBPD Hotline at (909) 384-5656.