Brooke Skylar Richardson, now 20, insists the baby was stillborn, claiming she buried it out of respect and grief behind her home in Warren County, Ohio in May 2017.
But prosecutors said Richardson killed the child, fearing it would ruin her life.
Now, Richardson is on trial for the incident that occurred while she was reportedly a popular cheerleader at Carlisle High School in Ohio.
No one knew Richardson was pregnant in the months leading up to the baby's arrival, except Richardson and her gynecologist, prosecutors said.
Her baby bump reportedly did not show in her cheerleader uniform or the red dress on prom night, which she wore two days before the newborn was buried.
The baby came in the middle of the night on May 7, 2017. Richardson's parents and brother were sleeping, prosecutors said.
Police eventually found out about the baby's death after Richardson's gynecologist reported the baby's death to the Warren County coroner, but left the cause of death blank.
Richardson is now charged with aggravated murder, involuntary manslaughter, endangering a child, tampering with evidence, and gross abuse of a corpse as a jury will left to decide how the newborn died.
Charles Rittgers, Richardson's attorney, said that his client learned she was pregnant at 37 to 39 weeks pregnant. She had just begun a relationship with her new boyfriend and went to talk to the gynecologist about birth control – but the gynecologist told her she could not have birth control because she was pregnant.
The doctor, who was bound to keep Richardson's pregnancy quiet upon her request, said she would likely have the baby within ten weeks, although it came 11 days later.
Rittgers said when the baby came it was lifeless and pale, the umbilical court was detached, and it was not breathing. After grieving for hours, she used a small shovel to dig a hole between two pine trees in the family's backyard and put the body inside.
Initially police believed Richardson's story that the baby was a stillborn, but a doctor brought into the case as an expert witness said the baby's bones looked charred, like the body had been burned.
The doctor later recanted the testimony and said she made a mistake – but Richardson was already indicted.
In an exhausting interrogation session, police got Richardson to say she burned the baby after she denied it 17 times and said the baby was stillborn 29 times.
Rittgers said:'What happens when that doctor who made this horrible mistake changes her mind and tells everyone I was wrong, the bones weren't burnt?’
‘What happened? The police didn't hit a reset button. The prosecutors didn't hit a reset button. . . . They disregard all truth that does not fit into their story. And that's why we're here today.’
Richardson's trial is expected to last two weeks as she faces life in prison if she is found guilty on all charges.