Why John Roberts cited the private papers of the justice who wrote Roe v. Wade

During Wednesday's historic oral arguments on abortion rights, Chief Justice John Roberts pulled back the curtain on internal Supreme Court negotiations and referred to the papers of the late Justice Harry Blackmun, the author of Roe v. Wade.

Roberts usually scorns any courtroom references to materials beyond the briefs and record of a case, let alone to private debate among justices. But he wanted support for his position that a key part of the 1973 landmark decision that gave women a right to abortion at the early stages of pregnancy could be scrapped without disturbing Roe's central holding.