Using a plastic baby doll as a prop, a former day care worker got down on the floor of an Arlington courtroom yesterday and demonstrated for a jury how Heidy Terceros force-fed milk to an infant in the home where she worked.

As the Circuit Court judge peered down from the bench, Roxana Patino held the doll's legs down firmly with her right leg, pretended to feed it from a bottle and then used an imaginary rag in her right hand to show how Terceros would force vomit back into the baby's mouth when she threw up her milk.

The infant girl "would turn purple and she would tremble," Patino, 31, testified tearfully through a Spanish interpreter. "I thought she was going to die."

The defendant, Terceros, 24, was missing on the opening day of her trial on charges of assaulting and abusing three children she helped care for in her mother-in-law's Arlington home. Prosecutors say the woman has apparently fled.

Over the objections of her attorney, David Bernhard, the judge started Terceros's trial without her, and Patino, who once worked with her, is the central witness in the case.

Also missing is Terceros's mother-in-law, Teresa Villarreal, 42, who is charged with three felony counts of child abuse. She failed to appear at an Aug. 19 hearing, and a warrant has been issued for her arrest. Although her passport was confiscated by the court, prosecutors fear she may have fled the country.

In a courtroom filled with parents of children who had been cared for in Villarreal's home on S. 12th Street, Deputy Commonwealth's Attorney Theo Stamos told the judge that prosecutors had no assurances that Terceros would ever be located.

Judge J. Howe Brown Jr. told prospective jurors yesterday only that the defendant was not present.

During opening statements, Assistant Commonwealth's Attorney Alejandra Rueda told the jury that Patino had witnessed the children--two infant girls and a toddler boy--being abused by Terceros in the home where they were cared for between July and October 1998.

Patino, an illegal alien from Bolivia who was hired by Villarreal in May 1998 and left in October, told her next potential employer how the children were force-fed and punished when they wouldn't eat, Rueda said. That person, a federal prosecutor, reported it to police, she said.

As the prosecutor described for jurors how the children were abused, their parents were kept outside the courtroom because they may be called as witnesses.

The nearly 3-year-old boy was hit on his back when he wouldn't take his nap, Rueda said, and finicky eaters were force-fed with their tiny arms strapped into an infant car seat. When they would cry and spit it back, Terceros would hit the child on the feet with adult shoes, use her fingers to flick the child's head and worse, she said.

"She would force the vomit back into the child's mouth," Rueda said. "The child would make choking noises."

Rueda told the jury that Terceros, who is charged with one count of felony abuse and two misdemeanor assault charges, endangered the lives of the children even though the alleged abuse was never detected by the parents.

Bernhard hammered that same point, that "no parent called police to say they suspected abuse." He also questioned Patino's motives in the case, accusing her of spinning "wild" stories about her former employer and Terceros. Patino is not a credible witness, he said, because she lied about her marital status at a preliminary hearing for Terceros.

He predicted that when jurors begin their deliberations, which they are expected to do today, they will come to the same conclusion: "We really don't know what happened."