Solution

The criminal finally admitted to committing this crime...

The criminal is Mrs. Janie Kinston. (Suspect #3)

She said for her alibi that she was arranging an upcoming volleyball game at University of Alabama on December 1, 2013. She said the game was 2 weeks from that date.

Then when you see the dates of the Alabama volleyball games, you see dates such as, 12-5-13. If the game was when she said it was planned for, the date would have been on 12-15-13, because that is 2 weeks from 12-1-12, which is not one of the dates Alabama played.

That means she was the only person that was free on the time when the crime was commited.