A Gaithersburg woman was convicted for the second time yesterday of leaving her three youngest children -- 18-month-old twins and a 4-year-old girl -- alone in what a prosecutor called a "subhuman house" littered with feces, flies, spoiled food and garbage.

Cynthia D. Retherford, 34, a food store cashier and mother of six, was convicted by a Montgomery County Circuit Court jury of one count of contributing to the negligence of the three children and two counts of leaving a child unsupervised by a person 13 years of age or older.

The three younger children have been in foster care since August, officials said. The three oldest children, 13, 14 and 16, remain in the home.

Retherford, who is free on bond pending sentencing April 12, could be sentenced to more than three years in prison.

Yesterday, Circuit Court Judge J. James McKenna, who presided over the two-day jury trial, told Retherford, "Woe be to you if any report comes back to me that you have a house of hell."

The jury deliberated about five hours over two days. Prosecutor James Trusty asked the jury to hold Retherford accountable for the devastation in the house. "This is not short-term mistakes or sloppy baby-sitting, but long-term neglect," he said.

Police were called to Retherford's town house off Clopper Road on July 28 when a visitor to the complex saw the twin girls screaming and crying in a window. A police officer testified there was "wall-to-wall" debris in the house, which reeked of urine and garbage. The two toddlers were covered with feces, flies and insect bites, the officer said.

Retherford, a widow, testified Tuesday that she was "shocked and horrified" by the squalid conditions in the house. She said she had left her 14-year-old daughter to care for the children. "I've never seen them look like this in my life," she sobbed, while reviewing photographs of the toddlers. "This is awful. I can't tell you what happened."

Retherford's attorney, Robert Matty, urged the jury not to judge his client by television stereotypes. "She's not Donna Reed. Her family is not the Brady Bunch," he said. Matty said Retherford was an overwhelmed mother "trying to make a go of it on limited resources."

Yesterday's verdict was the second conviction for Retherford on the same child neglect charges. After a trial in September, District Judge James L. Ryan found Retherford guilty of three counts of child neglect and three counts of contributing to the negligence of a minor.

Ryan sentenced Retherford to three years in prison, but suspended all but 30 days and placed her on supervised probation for one year. Retherford appealed Ryan's decision and was granted a new trial in Circuit Court.