Ariel Castro, 52, could face the death penalty if convicted of the aggravated murder charge, which is a capital offence in Ohio if it occurs in connection with a kidnapping.
Castro's lawyer entered the plea on his behalf in a brief arraignment. He shuffled into the courtroom in an orange prison jumpsuit with his head bowed and did not say a word.
The stunning case came to light after Amanda Berry, 27, managed to escape with her six-year-old daughter by calling out to a neighbour for help through a locked front door.
Ariel Castro, 52, could face the death penalty if convicted of the aggravated murder charge, which is a capital offence in Ohio if it occurs in connection with a kidnapping.
Most US states have foetal homicide laws which allow prosecutors to punish those who harm pregnant women while also protecting the woman's right to carry out a lawful abortion.
Kidnapping and rape are not capital offences despite the horrifying ordeal imposed on the three women who were snatched off the street with a promise of a ride home at the ages of 14, 16 and 20.
