Baby Gabriel's Mother Due Before an Ariz. Judge Today

Jan. 25, 2010— -- Elizabeth Johnson, the mother of missing 8-month-old Gabriel, is due before an Arizona judge today when she is expected to plead not guilty to charges that include kidnapping, child abuse and custodial interference.

Johnson, 23, and the boy's biological father, Logan McQueary, were in the middle of a custody dispute when she fled Arizona with Gabriel before Christmas. Johnson allegedly sent text messages to McQueary, saying she had killed their son and left his body in a trash bin.

She later changed her story and said she gave the baby to a random couple she met in a San Antonio park. Police have not been able to confirm that that couple exists.

Another Arizona couple who said they were in talks with Johnson to adopt the baby said they also had no idea of his whereabouts, although police have named them as persons of interest for potentially withholding information.

McQueary held a vigil last night in Scottsdale, Ariz., with his friends and family. He said he still holds out hope that his son, who has been missing for more than a month, will be found alive and returned home safely.

"I hope he comes back soon," McQueary said. "I want him back more than anything else."

Johnson has refused to speak to investigators, which has put them and the prosecution in a difficult position.

"It's the dilemma of, you have somebody incarcerated but you really need their help in finding this baby, and so the real key is communication between the police and Elizabeth because that relationship will get you that piece of information that you need," Brad Garrett, an ABC News consultant and former FBI agent, said.

Gabriel 's babysitter, Analisa Urias, one of the last known people to see the missing baby, said he seemed sad and frightened the night she took care of him in a Texas hotel room.

Johnson hired Urias through a Craigslist ad to babysit Gabriel while she was escaping the custody dispute.

"Elizabeth told me if anyone came knocking on the door, not to answer it," Urias told ABC News.

Tempe, Ariz., police released the photographs of Gabriel taken by Johnson in the same Texas hotel room in hopes it would help them find the missing baby.

Although Gabriel appears to be healthy and active, lying on a bed with toys and a pacifier, investigators fear that Gabriel is holding a medicine dropper in two of the photos.

"Elizabeth told me to give him a bottle in about an hour and then her exact words were to 'Give him more medicine if he started crying to shut him up,'" Urias said.

"Gabriel wasn't acting like a normal baby," she said. "He was acting scared, he didn't want to play. He acted like he was sad."

The photographs were found on Johnson's camera following her arrest Dec. 29 in Miami.

In another claim, Urias said she found a large knife next to the bed in the motel room.

"It looked like a butcher type of knife and, you know, I thought that was weird because why would she have it next to her bed? It's something that would belong in the kitchen," Urias said.

The photographs were date-stamped Dec. 26, the last day anyone saw Gabriel.