Correction: It was Supreme Court Justice Stanley Reed [1], not Chief Justice Earl Warren [2], who "expressed concern that if the Court's power became too widespread, America would have, instead of democracy, kritarchy". He did so in late July 1953, specifically regarding the not-yet-decided Brown v. Board of Eduction decision of May 1953, in a discussion with one of his law clerks, John David Fassett. He confronted Fassett with the question, "Are you one of those people who believes in krytocracy?" Apparently, he discussed this question at length with his law clerks in the months leading up to the Brown decision. I could find no evidence that he spoke with his Supreme Court colleagues about it, but, then again, I've done no real research.

Also according to Fassett, in a February 1953 memo--three months before the Brown ruling--fellow Supreme Court Justice Robert Jackson [3] used the term "a ruthless use of judicial power." Although Jackson did not use the term "krytocracy," Fassett commented, "That was sort of Justice Reed's feeling too--his krytocracy thought was the same thing."

I found all of the above in this article [4].

Finally, it is worth noting that, regardless of certain Justices' concerns about the Constitutional limits of judicial authority, the Brown v. Board of Education ruling overturned Plessy v. Ferguson by a unanimous vote, 9-0.

[1] https://en.wikipedia.org/wiki/Stanley_Forman_Reed

[2] https://en.wikipedia.org/wiki/Earl_Warren

[3] https://en.wikipedia.org/wiki/Robert_H._Jackson

[4] http://www.roberthjackson.org/files/theman/speeches-articles...