KANKAKEE, Ill. (CBS) – A grandmother in Kankakee will spend New Year’s worrying if she’ll get sent back to prison.

She was convicted some 15 years ago of shaking her grandson to death.

“Prison is so horrible. It’s just so horrible,” Shirley Smith says.

The 51-year-old served 10 years in prison and was freed, but recently learned she may have to go back behind bars on a conviction for allegedly shaking her grandson to death.

“I didn’t do what they said I did,” she says.

Back in 1996, Smith left Illinois for California to help her daughter, Tomeka, care for her three children.

Smith says 7-week-old Etzell Glass had fallen off of a sofa where he was sleeping with his 14-month-old brother that tragic night.

“I woke up to my two grandsons crying. They were both on the floor. I picked both of them back up,” she says.

Smith says she later came back to find baby Etzell’s lifeless body.

His sister Yolanda was just three years old and can’t even remember his face.

An autopsy showed the baby died of Shaken Baby Syndrome, with some blood on his brain. But Smith says none of the other typical shaken baby indicators were there.

“There was no bruises or abrasions,” she says.

But a jury still convicted her. In 2006, a federal appeals court granted smith a release from prison, saying there was “no demonstrable support” for a shaken baby conviction.

But in October, the U.S. Supreme Court decided overturning the conviction was wrong and that smith should go back to prison.

Smith hopes the governor of California will grant her clemency.