In late 1966, New Orleans District Attorney quietly opened an investigation into local aspects of the Kennedy assassination. Local reports soon got wind of this, and in early 1967 the investigation quickly gained a national spotlight. Garrison arrested New Orleans businessman Clay Shaw and charged him in the murder of the President. The case went to trial in 1969 and Shaw was acquitted.
Available here is not only the transcript of the Clay Shaw trial, but also grand jury records which had been ordered destroyed at one time, but which were delivered safely to the Assassination Records Review Board in the mid 1990s.