Court of Crows is a court drama originally published in 1961 in hardcover and then published at least twice in paperback by Popular Library, in 1963 and 1967. Although reviewed in the New York Times when released it is so unknown today as to not even be found on Goodreads.
From the back cover "A fascinating journey into the devious twistings of adultery, murder and betrayal among a decadent people..." and "...because she was an adulteress, she stood trial for murder...an impressively substantial novel..."
There are a fair number of copies available on the secondary market. Fourteen copies on Biblio, for example, as low as $5.99.
Information on Knowlton himself is harder to find. He was an officer in the Navy and an editor at the United Press. Born in 1914, he died young in 1968. His father was a well-known trial lawyer in Massachusetts.
Me as a critic (be careful! the harshness will be well concealed!)