A 16-year-old Michigan girl pleaded guilty Friday to second-degree murder for poisoning her grandmother with morphine.

Kristina Adkins entered the plea in a packed courtroom in the southeastern Michigan town of Adrian. She was only 13 in 2006, when 53-year-old Virginia Bentley was poisoned.

The girl's attorney, Mike McFarland, said she turned to poison because she was mistreated by her grandmother.

Prosecutor Jonathan Poer was not immediately available for comment.

Because of her age, Kristina could receive a maximum life term as an adult, but a judge could consider her juvenile status as well and choose lighter punishment at sentencing on Oct. 31.