Gabriel Johnson has been missing for more than a month, and police say they are not optimistic the baby is still alive.
Before arresting Tammi Smith, 37, Tuesday, police had searched the Scottsdale, Ariz., home she shares with her husband, Jack. Smith was charged with conspiracy to commit custodial interference, custodial interference and forgery.
According to local CBS affiliate KPHO, Smith told police that she and her husband planned to adopt Gabriel from his mother, Elizabeth Johnson, but that the boy's biological father, Logan McQueary, would not go along with it. Police say Smith provided wrong information on custody paperwork, falsely identifying Gabriel's father.
Johnson, 23, was last spotted with her son on Dec. 26 in San Antonio, KPHO reported. Shortly afterward, Johnson sent a text message to McQueary, telling him that she had killed their son, police said. Four days later, Johnson was arrested in Miami.
Johnson was extradited back to Arizona and remains in a Maricopa County jail cell. She has pleaded not guilty to charges of kidnapping and custodial interference. Police say she told them she gave the boy to a couple she met at a park in Texas, KPHO reported.
In hopes of finding his son alive, McQueary embarked on a road trip to retrace his estranged girlfriend's route to Miami. He received the news of Smith's arrest on the way to San Antonio, where investigators have recently begun searching a landfill site for possible clues.