Zoraida Magali Conde Hernandez was on her way to pick up diapers before she got her 8-month-old son from his Head Start program July 5. She had just picked up her 2-year-old, Emily, at day care, and the girl was throwing a tantrum.

When Conde Hernandez reached around to deal with her daughter, according to detectives, she saw a tiny foot poking out of the other car seat.

Conde Hernandez, 32, told police she thought she had dropped baby Nathan off hours earlier, before work. In fact, he had been in her car all day. She pulled over. Nathan was purple. She brought him to Inova Alexandria Hospital, but he was dead.

A grand jury will hear the commonwealth’s case against Conde Hernandez for felony child neglect, an Arlington judge ruled Monday.

“I don’t know how she could miss the child,” Judge Esther Wiggins said. “It was her responsibility to make sure the child was okay.”

A police officer testified that Conde Hernandez was “forlorn” and “very emotional” when she was interviewed at the hospital. While waiting for detectives, the mother showed the officer pictures of Nathan, saying, “He was a happy child.” She was arrested soon afterward.

Conde Hernandez had been raising five children, with help from her boyfriend and parents. Now, she cannot see her children without supervision.

The ruling was expected, as is a grand jury indictment. Defense attorney Rebecca Wade remains confident that her client will not be convicted.

“We need to be in the trial court,” she said. “That’s where we’ll get a not guilty verdict.”

Several family members and a colleague from the Catholic Diocese of Arlington, where Conde Hernandez is an administrative assistant, were at the court appearance. Friends from the church are raising funds for her legal defense.

Also attending was Lyn Balfour, whose son died six years ago in a similar accident. After the hearing, she spoke quietly with the defendant.

“I told her the pain never goes away,” Balfour said. But Balfour also told her that “she didn’t do anything wrong” and that a jury would agree. “People see that. They understand.”