On January 5, 1930, Sonia Ragins, age 26, died from an illegal abortion performed at an unknown location by an unknown person. On January 6 the coroner recommended identification and arrest of the guilty party.
The "unknown perpetrator" phenomenon didn't go away with legalization. Many of the abortion deaths I've researched, nobody knows who -- at an openly operating abortion clinic or hospital -- performed the abortion. The families have to sue all the doctors as a shotgun approach to hope they're suing the one who killed their loved one. Sometimes they don't even have a list of doctors to sue, and they have to resort to suing a John Doe abortionist and hope that the facility will identify him during their blame-shifting.
And there are also abortion deaths classified as "unknown" whether they were legal or illegal because nobody's able to determine where it was performed, much less by whom. Because these deaths are only a public health matter, not a criminal matter, there's no impetus to track down the offender.