Phoenix (CNN) -- An Arizona jury found Tammi Smith guilty of forgery and conspiracy to interfere with custody Thursday in the 2009 disappearance of 8-month-old Gabriel Johnson, whose whereabouts remain unknown.
Smith was accused of trying to help Gabriel's mother, Elizabeth Johnson, wrangle custody of the boy from his father, in order to adopt the little boy herself. She faces a pre-sentencing hearing in June to determine whether she will serve prison time, and formal sentencing July 6.
Smith maintains her innocence and will appeal Thursday's verdict, her lawyer, Benjamin Taylor, told HLN's "Prime News."
"We're disappointed in the verdict and we're going to move on with our life and go from there," he said.
Johnson is still awaiting trial on charges of kidnapping, custodial interference and child abuse. She allegedly told the father she killed the infant and put his body in a garbage bin, but later told police she drove from her home in Arizona to Texas and gave him to a couple she met in a San Antonio park.
She later told police she handed over the child under Smith's direction, and prosecutors said Smith falsely wrote the name of her cousin on a paternity document as Gabriel's possible father.
Smith maintained she did not know where the child was, and that she had nothing to do with the couple who supposedly received Gabriel.
Frank McQueary, the boy's grandfather, said the family's hopes of finding the child alive are fading.
"Nobody has seen Gabriel for almost three years now," McQueary told HLN. "It's been a long time, and I just don't think there's anyone out there hiding this baby at this point."
In Session's Beth Karas contributed to this report.