Johnson's body was found Friday in Curry-Demus's apartment. The body was positively identified through dental records, Allegheny County Medical Examiner Karl Williams said Sunday.
In the criminal complaint, police said that video surveillance at the Allegheny County Jail from Tuesday afternoon shows Curry-Demus talking with Johnson for several minutes. The women were at the jail visiting different inmates, police said.
The clothing Johnson is seen wearing on the surveillance tape was consistent with the garments found on her body, police said.
Allegheny County Police Superintendent Charles Moffatt said the jail was the last time Johnson was seen alive.
Curry-Demus was being held in county jail on Sunday and it was not immediately clear whether she had an attorney. A lawyer who had represented her previously did not immediately return a phone message left Sunday.
No one was home at the McKeesport home of Johnson's father on Sunday.
In the criminal complaint, police said Johnson's body was found bound at the wrists and ankles with duct tape, and there were layers of duct tape and plastic covering much of her head. Her body was wrapped in a comforter and garbage bags and placed under the headboard of the bed in the master bedroom.
Williams said Johnson appeared to have been dead for about two days. She "had a wound to the abdomen consistent with the removal of a baby," Allegheny County Police Superintendent Charles Moffatt said.
"A very sharp instrument" was used to cut open Johnson's belly, he said.
Authorities said Johnson was 36 weeks pregnant, and they were trying to determine whether she was alive when the baby was removed. They also are awaiting toxicology tests to find out whether she was drugged. Test results are not expected for several weeks.
Police said in the complaint that Curry-Demus denied meeting Johnson but that she told investigators that her fingerprints would be on the duct tape and plastic used to wrap the body.
Curry-Demus showed up at the hospital Thursday with a newborn that still had the umbilical cord attached, police said. Tests later proved that she was not the mother.
Police said Curry-Demus initially told investigators she bought the baby for $1,000 from the its mother. She later said two people brought a pregnant woman to her apartment Tuesday evening, removed the baby the next day and gave it to her. She said she then took the newborn to her sister's apartment and told her she had just given birth, police said.
Curry-Demus' sister told investigators she didn't see anyone else in Curry-Demus' apartment when she visited twice Wednesday morning, police said. On the first occasion, Curry-Demus repeatedly went into the bedroom alone, closed the door and stayed there for several minutes. On the second occasion, Curry-Demus showed her sister the baby and claimed to have just given birth, police said.
Wilkinsburg Police Chief Ophelia Coleman said Sunday the child was "under observation." Williams earlier said the baby was "apparently doing well." The hospital has declined to release any information about the child.
In 1990, Curry-Demus, then known as Andrea Curry, was accused of stabbing a woman in an alleged plot to steal the woman's infant. A day after that stabbing, Curry-Demus snatched a 3-week-old baby girl from a hospital after the child's 16-year-old mother had gone home for the night. The baby was found unharmed with Curry-Demus at her home the next day.
Curry-Demus pleaded guilty in 1991 to various charges from both incidents and got three to 10 years in prison, according to court records. She was paroled in August 1998.
