It goes like this ... young unmarried JW girl, Mary, falls pregnant. Elder Matthew and Elder John, after consulting with Elder Mark, conduct initial judicial investigation.
Young unmarried JW girl, Mary, denies having sex with her fiance, Joseph, who himself denies having sex with Mary.
The elders convene and offer a prayer to jehovah for guidance so as to remove the unknown fornicator from the congregation.
A short time later jehovah comes clean and says "It was me. I got Mary pregnant even though she was engaged to Joseph at the time. I wanted a son."
The body of elders ring the Watchtower legal department to report the rape of Joseph's fiancee.
Watchtower legal ask "Were there two witnesses?" The elders reply "Well jehovah admitted to impregnating the fiance of Joseph."
Watchtower legal replies "Hmmm. Considering that Mary has denied committing fornication, then no sin has been committed as there are no two, or more, credible witnesses."
As for Elder Luke, he's not credible as he was never there nor part of the judicial committee.
Problem solved. And the rest is history...
By the way, under the Mosaic law the punishment for getting Mary pregnant, while engaged to Joseph, was death. Remember, Joseph, after finding out that Mary was pregnant, went away to get a secret divorce.