<p>A baby girl was fatally stabbed Friday morning on the Southwest Side, and a suspect who leaped from a window to escape is in custody. </p><p>Nyhnia Stovall was inside a home in the 3000 block of West 59th Street when a "known offender" used a knife to stab her in the chest about 7:20 a.m., police and the Cook County medical examiner's office said. </p><p>Nyhnia, not yet a year old, was taken to Comer Children's Hospital, where she was pronounced dead, the medical examiner's office said.