What is the ruling on the lineage and status of the child if the usurper was ignorant and impregnated the slave girl?

Primary text

If the usurper was ignorant, the resulting child is free (Hurr), attributed to his lineage, because of his belief that he was having intercourse with his property, and this belief establishes a legal doubt. If she gives birth to a dead fetus, he is not liable as he was unaware of its life. If she gives birth to a living child, he owes its value on the day of birth because that is the first moment its value can be assessed and the moment the separation between the child and its owner is established.