Though there were useful exceptions,* often in concurring and dissenting opinions, the Supreme Court often did not go into much detail when discussing why there is a constitutional right to privacy. This addendum will suggest a few reasons.
First, Griswold v. Connecticut reflected Douglas' standard policy of thinly argued opinions that were often conclusionary. This did not mean he couldn't spell things out. In fact, he repeatedly did, including on this very subject (if not as expansively as the now seminal dissent of Harlan) in his Poe v. Ullman dissent as well as in other writings. It is sometimes suggested Brennan encouraged him to take the approach in Griswold, but a lecture he gave a few years before had the basic idea, down to the use of "penumbra." A more careful thinker might have got more than personal value from opinions that toss in comments like (in a ruling shortly before Roe):
The difficulty is that these activities are historically part of the amenities of life as we have known them. They are not mentioned in the Constitution or in the Bill of Rights. These unwritten amenities have been in part responsible for giving our people the feeling of independence and self-confidence, the feeling of creativity. These amenities have dignified the right of dissent and have honored the right to be nonconformists and the right to defy submissiveness. They have encouraged lives of high spirits rather than hushed, suffocating silence.
Second, Blackmun was just starting out when he wrote Roe v. Wade, and was not much of an opinion writer either. Accounts, such as The Brethren, suggests he insisted to work on the opinion mainly by himself, and the emphasis on history and medical matters reflected his comfort area as a lawyer for the Mayo Clinic. As noted, his excellent Bowers dissent that flesh out the right to privacy was greatly the work of Pamela Karlan. The material was there for a better opinion in Roe as well, even with amateurs leading the way (Sarah Weddington was in her 20s), especially given various briefs help out.
Third, there was a certain charm in thinly argued opinions that had some key broad phrases since fleshing things out might cause problems (as one lower court opinion noted, the basic idea of Griswold was agreed upon, even though the reasoning was split). Relatedly, the Supreme Court was pretty results orientated in the 1960s and early 1970s, so reasoning was not really its thing. Brennan, a leader at the time, did not really care about specific details. Douglas' more expansive concurrence in Doe v. Bolton had an outline that reflected a memorandum give to him by Brennan [see Liberty and Sexuality] but Brennan never wrote or joined an opinion that expansive in detail. This is unfortunate since one duty of the judge is to explain their reasoning, and if some of it is only implied, the value of opinion writing is reduced. This always occurs in some fashion, of course.
And, once the basics of a "right to privacy" was established, as it was in Griswold, further in depth discussion of its origins and specific constitutional backing was apparently not really deemed necessary. This is unfortunate, since it was a big step (if one that -- as I have repeatedly said here and elsewhere -- with firm grounding) to firmly announce such a right. It bore repeating how freedom of expression, conscience, association, privacy reflected in the Fourth Amendment, freedom from self-incrimination (in its broadest form), liberty related to basic freedom and freedom from slavery leads to the right to privacy. Equality is interconnected here as well, one essay in the book referenced last time underlining how freedom to make private family matters often is essential to black women in particular.
Griswold said as much in bare bones form, but since few seem to deign to read its reasoning (focused only on result -- leading Scott over at Lawyers, Drugs and Money to suggest few really care about judicial reasoning, a bit exaggerated, but true enough to help explain things), the point clearly warrants further emphasis. This is true also if one wants to focus on "liberty" over some "right to privacy" in particular, which is the preference of some and the emphasis of Justice Kennedy in particular. The tools are there as is the audience: many are quite open to the results, so providing some analysis would be welcome as well.
Again, I don't mean to exaggerate and say that the rights in question were not analyzed at all. But, people criticize the opinions with some reason, and it is useful to get the whole story out.
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[footnote added]
* In an otherwise minor case upholding a prescription drug database, Justice Stevens authored an opinion a few years after Roe joined by all justices that provided a useful summary of the "right to privacy," at one point quoting this analysis:
The concept of a constitutional right of privacy still remains largely undefined. There are at least three facets that have been partially revealed, but their form and shape remain to be fully ascertained. The first is the right of the individual to be free in his private affairs from governmental surveillance and intrusion. The second is the right of an individual not to have his private affairs made public by the government. The third is the right of an individual to be free in action, thought, experience, and belief from governmental compulsion.
"Private" doesn't simply mean anonymous; the public knows various things about what you do or who you invite to your home, which is "private" property. I stick to my feeling that the concept has merit, "liberty" too open ended, things like "autonomy" a bit too obscure. And, to the degree some need help to fully enjoy their rights (e.g., funding), that just means it is not a one note thing. Does needing help to enjoy a family mean decisions involving it are not basically private?
Justice Stevens expands on the concept [FN11], but "how he will live his own life" is his bottom line, which sounds like "privacy" to me. Sure, equal protection etc. factor in, but few rights stand alone. On the Fifth Amendment, see also here, FN12/13 and surrounding text, cited by Stewart in his Whalen concurrence.