Jennifer Del Prete was convicted in 2005 for the murder of Isabella Zielinski. Prosecutors contended Del Prete violently shook the little girl while working at a suburban Chicago day care facility. She was given a 20-year sentence.
On orders from U.S. District Judge Matthew Kennelly, the 43-year-old Del Prete was released Wednesday from Logan Correctional Center.
Kennelly wrote the woman's case was "exceptional and deserving of special treatment" because she has "substantial" evidence of innocence. He said it could take years for her to clear her name.
Will County State's Attorney spokesman Charles Pelkie said last week prosecutors remain confident in their case against Del Prete.
For almost a decade, Tia Del Prete has waited for her mom to walk out of prison.
"Everyone that's fought for this and fought for her and believed in her, we'll really feel all their love at that moment I think," said Tia Del Prete.
Del Prete maintained her innocence and nine years after Isabella's death, she went to prison. Her case caught the attention of Northwestern University's Medill Justice Project.
"The infant had internal head injuries, but there were no external signs of abuse. There were no grip marks, no bruising, no broken bones, no injured neck," Professor Alec Klein, Medill Justice Project, said.
Further investigation revealed a letter from a Romeoville police detective that was not introduced at trial or shared with Del Prete's attorney, Klein said.
"In this letter, the detective said that he was worried that because the doctor who did the autopsy had grave doubts about whether the child was a victim of shaken baby syndrome," Klein said.
On the basis of that letter, Del Prete's conviction is being appealed. Federal Judge Matthew Kennelly said ". . .more likely than not that no reasonable juror would have found her guilty of murder beyond a reasonable doubt."
The judge ruled last week that Del Prete can be released on bond while her conviction is appealed.
"I was crying of happiness like I am now," Tia Del Prete said. "I can breathe again. Everything feels right."
The Associated Press contributed to this report