TULSA, Oklahoma - New evidence could free a Tulsa mother, who's been in prison for 20 years for slitting her three-month-old baby's throat. Michelle Murphy's attorney said there was blood at the scene that doesn't match Murphy's.

The possible evidence would have remained in the dark had it not been for one of Murphy's former teachers. That teacher has said Murphy is innocent since day one, and she has made it her mission to make sure the young mother is a free woman.

In September of 1994, a three-month-old baby was found lying in a pool of blood with his throat slashed. His 17-year-old mother, Michelle Murphy, was arrested and convicted of killing her child, but she has always maintained her innocence.

"I firmly and totally 100-percent believe in her innocence and it's been a very tragic thing," said Murphy's former teacher, Susan Jones.

Jones calls the ordeal a nightmare.

"I was the one to go and visit her the whole time. I just kind of got involved from the very beginning. We became like friends, then like sisters and now it's kind of like a mother daughter relationship."

Five years ago, Jones decided it was time to find the evidence to set Murphy free. Murphy's new lawyer said Type AB blood samples found at the crime scene do not match Murphy or her son.

The attorney believes DNA tests could prove the blood belongs to the prosecution's star witness, William Lee, who committed suicide before the case went to trial.

Now, Murphy is asking a judge to compare the blood at the scene with Lee's DNA on file at the medical examiner's office.

"We're making progress every day. We're making progress and we're getting closer to the end result," Jones said.

She said that the end result is seeing Murphy released from shackles and set free.

"Oh my gosh, I can't wait," said Jones. "I can't wait to introduce her to the world. My husband and I are going to be bringing her into our home and transitioning her back into society, into the world."

Murphy's attorney wants the DNA samples to be tested in a lab of his client's choice. On Friday, a judge is expected to decide which samples will be tested and where they will be tested.