Dear Ms. Harris,
Thank you for posting your request on History Hub!
We suggest that you contact the State Library and Archives of Florida to request a search of the Inactive case files, 1941-1960 of the Florida Parole Commission for any amicus curiae briefs filed under Walter Irvin.
We searched online and located Irvin v. State :: 1953 :: Florida Supreme Court Decisions and The Law of the Groves: Whittling Away at the Legal Mysteries in the Prosecution of the Groveland Boys that also may be useful.
We hope this is helpful. Best of luck with your research!