(CNN) The Supreme Court's landmark decisions guaranteeing a constitutional right to abortion emerged only after surprise votes and last-minute compromises. They were also the product of individual soul-searching and broad regard for the court. And, perhaps reflecting a different era, they were steered by Republican appointees who believed privacy rights covered a woman's decision to end a pregnancy.
The private papers of justices who resolved those cases reveal the negotiations behind the decisions, including how the justices developed the cutoff line for when a state's interest in prohibiting abortion could surpass the woman's interest -- a flashpoint in today's debate.
It was not until the final weeks of drafting in the 1973 Roe v. Wade case that the justices settled on the point of viability, that is, when a fetus can live outside the mother's womb, now considered at about 22-24 weeks.
The court will revisit that constitutional test tied to fetal viability on December 1 when it hears the challenge to a Mississippi law that would ban abortion after 15 weeks of pregnancy.
In the balance lie women's reproductive rights and the scope of constitutional privacy protection. The case will lay bare the direction of the evolving court under Chief Justice John Roberts, perhaps to make the most significant departure yet from courts back a half century.
Justice Harry Blackmun, writing the Roe opinion, at first considered the end of the first trimester of pregnancy (at about 12 weeks) as a dividing line. He was persuaded to delay that cutoff, by roughly another 12 weeks, after an initial suggestion by Justice Lewis Powell and reinforcement by others in the Roe majority.
Blackmun himself explained as he prepared to amend his views that viability "has logical and biological justifications."
"There is a practical aspect, too," he continued in a memo to fellow justices, "for I am sure that there are many pregnant women, particularly younger girls, who may refuse to face the fact of pregnancy and who, for one reason or another, do not get around to medical consultation until the end of the first trimester is upon them or, indeed, has passed."
Some of that history has surfaced in "friend of the court" briefs in the Mississippi case and may be mined by the justices as they take up the most important abortion case since 1992, when the court affirmed Roe in Planned Parenthood of Southeastern Pennsylvania v. Casey. The court had grounded the right to end a pregnancy in the Fourteenth Amendment's due process guarantee of personal liberty.
Overall, the now-public archives of justices who decided the two momentous abortion cases demonstrate individual soul-searching, as well as larger regard for the integrity of the court.
The times were not as polarized, and Republicans played leading roles in crafting the decisions. Roe was decided by a 7-2 vote. Yet the decision was not pre-ordained. Justice William Brennan wrote in his personal account of Roe, available in his papers at the Library of Congress, that initially "it looked extremely doubtful that there would be a majority for the position that restrictive abortion laws are unconstitutional."
Nearly 20 years later, similar tensions and uncertainty shrouded the dispute of Planned Parenthood v. Casey, which was a direct challenge to the right to obtain an abortion. Justices Sandra Day O'Connor, Anthony Kennedy and David Souter -- all nominated by Republican presidents -- worked secretly at first, without consulting other colleagues, to forge a compromise that would affirm Roe.
Their decision, joined by two other justices and over the dissent of four others, declared that Roe's "essential holding ... is a recognition of the right of the woman to choose to have an abortion before viability and to obtain it without undue interference from the State."
O'Connor, the country's first woman justice, said from the bench when the case was handed down, "Some of us as individuals find abortion offensive to our most basic principles of morality, but that can't control our decision. Our obligation is to define the liberty of all, not to mandate our own moral code."
Abortion cases count among the most wrenching for the court, stirring religious, cultural and economic interests. In the early 1970s, before Roe v. Wade, some states were beginning to legalize abortion, but nationwide momentum was slow because of religious opposition, notably from the Catholic Church.
When Roe was decided, Brennan was the only Catholic justice. Today, six of the nine justices are Catholic.
The Roe v. Wade controversy, arising from the plight of a Texas carnival worker who said she was raped, was first argued in December 1971 and considered by a seven-justice bench. (Justices Hugo Black and John Marshal Harlan had suddenly retired due to ill health.)
Once two new appointees of President Richard Nixon (Powell and William Rehnquist) had been confirmed, then-Chief Justice Warren Burger, a fellow Nixon appointee, pushed for re-argument so that they could be part of the decision. Blackmun, also a Nixon appointee, agreed, writing: "I believe, on an issue so sensitive and so emotional as this one, the country deserves the conclusion of a nine-man, not a seven-man court, whatever the ultimate decision might be."
Brennan, in particular, thought the addition of Powell and Rehnquist would diminish the chances for a decision finding a privacy right to abortion and wrote in his personal case history of the second round of oral arguments.
"The questions from the Bench seemed to indicate clearly that Justice Blackmun had changed his mind on the abortion issue and that Justices Rehnquist and Powell would make five for the views expressed last Term by the Chief Justice and Justice (Byron) White," that is, against a right to abortion, Brennan wrote.
"Nevertheless," Brennan continued, referring to the justices' private meeting after the oral arguments, "the vote at Conference was a surprising 7 to 2 in the Texas case." (Powell voted for an abortion right, Rehnquist against.)
When Blackmun sent around an early draft of his opinion on November 22, 1972, he explained that he had chosen the end of the first trimester of pregnancy to be the critical point after which a state could constitutionally regulate abortions. He said that in those first 12 weeks, the abortion decision should be kept between a woman and her doctor, without interference from government.
Powell wrote Blackmun a private note a week later, saying he believed that a woman's constitutional right to abortion, protected from state regulation, should extend deeper into pregnancy.
"I have wondered whether drawing the line at 'viability' -- if we conclude to designate a particular point in time -- would not be more defensible in logic and biologically than perhaps any other single time," Powell said in the note that is now in an archive at Washington and Lee Law School. "(T)he interest of the state is clearly identifiable, in a manner which would be generally understood, when the fetus becomes viable. At any point in time prior thereto, it is more difficult to justify a cutoff date."
A group of 13 constitutional law scholars highlighted that citation with other documents in a "friend of the court" filing this week as they urged the court to uphold "the viability line." They described it as "logical and workable, and one of the many lines this Court has drawn to protect constitutional liberties."
Back in December 1972, Blackmun expressed concern about keeping the full seven-justice majority for the viability cutoff. "I could go along with viability if it could command a court," he wrote to Powell on December 4. Archival materials demonstrate that after Blackmun sent a December 11 memo to his colleagues, they indeed endorsed using fetus viability as a dividing line.
Justice Thurgood Marshall wrote on December 12: "I am inclined to agree that drawing the line at viability accommodates the interests at stake better than drawing it at the end of the first trimester. Given the difficulties which many women may have in believing that they are pregnant and in deciding to seek an abortion, I fear that the earlier date may not in practice serve the interests of those women, which your opinion does seek to serve.
"At the same time, however, I share your concern for recognizing the State's interest in insuring that abortions be done under safe conditions. If the opinion stated explicitly that, between the end of the first trimester and viability, state regulations directed at health and safety alone were permissible, I believe that those concerns would be adequately met," he added.
Roe v. Wade adopted a trimester approach, with the second trimester focused on maternal health. Only during the third trimester could a state forbid abortion except when necessary to protect the woman's life or health.
Dissenting in Roe were Rehnquist and White, an appointee of Democrat John F. Kennedy. (Rehnquist went on to become chief justice in 1986 and dissented when the justices upheld Roe in 1992.)
Powell's private notes to his own file reflect the pride he took in persuading Blackmun to protect pregnant women through viability and his appreciation for a law clerk who helped him work through the issue, Larry Hammond.
Powell wrote to Hammond on January 3, 1973, about three weeks before Roe v. Wade would be handed down.
"It seems to me that Justice Blackmun has reached a constitutionally sound result and stated it clearly," Powell wrote. "Although he gives credit in his memo ... to others, I suggest that you are entitled -- particularly in view of your education of me on the viability issue -- to credit that is nonetheless substantial because it will never be recognized. I think I was perhaps the first to press for viability change."
None of the justices who decided Roe v. Wade are alive today, and Hammond, who became a prominent criminal defense lawyer in Arizona, died last year.
After the court announced Roe v. Wade on January 22, Brennan wrote: "Within a week, the letters were coming in at the rate of 2000-3000 a day and continued to do so at least a month. I, the only Catholic on the Court, and Justice Blackmun, the author of the opinion, received the bulk of the mail. The rhetoric and tone of the majority of the letters was extremely vitriolic."
The abortion debate only grew in intensity. Ronald Reagan ran for the presidency in 1980 against abortion rights. His administration (1981-1989) and then that of President George H.W. Bush (1989-1993) pressed the Supreme Court to overrule Roe v. Wade.
In 1992, it appeared that such pressure would succeed. But in Planned Parenthood v. Casey, Kennedy (a Reagan appointee) cast a crucial vote for abortion rights and maintaining the "viability" cutoff.
Kennedy had earlier staked out strong opposition to abortion rights, notably in a 1989 case when he joined a Rehnquist opinion attacking Roe v. Wade.
But Kennedy decided in the end that the matter should be left to a woman. In the joint opinion he signed with O'Connor and Souter in 1992, they affirmed Roe but dissolved the trimester framework and instituted a test that said government may not put an "undue burden" on a woman seeking to end a pregnancy.
An undue burden exists, and a regulation should be invalidated, "if its purpose or effect is to place a substantial obstacle in the path of a woman seeking an abortion before the fetus attains viability."
Those three justices conferred privately to develop the standard that affirmed Roe but gave states greater latitude for some regulations. In a personal note to Justice Blackmun, a month before the June 29 ruling, Kennedy wrote, "I need to see you as soon as you have a few free moments. I want to tell you about some developments in Planned Parenthood v. Casey, and at least part of what I say should come as welcome news." He told Blackmun that he believed it would "come as welcome news." (The note is in Blackmun's files at the Library of Congress.)
Kennedy, age 85, retired in 2018 and did not respond to a CNN request for an interview. Justice O'Connor, age 91, resides in her home state of Arizona and revealed three years ago that she is suffering from Alzheimer's Disease.
The third member of the crucial alliance, Souter, rested much of his decision on regard for precedent and that Americans had lived with Roe's protections for two decades.
"Despite the controversy it has produced, the decision has not proven unworkable in practice," Souter said, referring to Roe, as he spoke from the bench when Planned Parenthood v. Casey was announced. "It has undoubtedly engendered reliance and countless people who have organized intimate relationships and made choices that define their views of themselves and their places in society in the two decades since it was handed down."
Souter said such consistency was important for public confidence in the Supreme Court. "Like the character of an individual, the legitimacy of the court must be earned over time," he said.
Souter, 82, retired from the court in 2009 and returned to his native New Hampshire.
When contacted by CNN about Planned Parenthood v. Casey, he said he wanted "to be excused from voicing recollections of Casey."
Added Souter: "I still think that on a judge's past decisions his silence is the best course."