Updated

A suburban Chicago has pleaded not guilty in the stabbing deaths of her 7-year-old son and a 5-year-old girl she was babysitting.

Elzbieta Plackowska's (elz-BEE'-tah plah-KOW'-skuhz) stood silently in a blue jail uniform beside her public defender as he entered not guilty pleas on her behalf during the brief hearing in Wheaton on Wednesday.

Plackowska has told investigators that the children had been jumping on the bed at the girl's home in Naperville. She ordered them to pray, then stabbed them both dozens of times as they begged for their lives.

The 40-year-old Polish immigrant told investigators she killed her son because she was upset with her husband and was grieving her father. She said she killed the girl because she was a witness to her son's death.