From Hosty's Warren Commission testimony:
Representative FORD. When you say you made several other checks on the way to the office, did this involve----
Mr. HOSTY. Not in this case; other cases. I run anywhere from 25 to 40 cases any one time. I have to work them all, fit them in as I go.
Hosty's response of "25 to 40" cases was meant to excuse the time it had taken to open/shut and investigate cases. It is the typical excuse offered by any government case-worker - "my caseload is too high!"
But what here are the facts. It was in Hoover's interest to present the best case possible to Congress that he needed more money - more case officers...
So in 1962, Hover's submission for his 1963 budget was that his officers currently carried around 22 cases each.
In 1963, he was quoted as stating that 20 cases per agent would be "too high".
Today in an average sized field office it would be in 15 to 20 range.
Hosty's claim of having 25 to 40 cases to juggle at any one time appears to be an exaggeration - as a matter of CYA, even allowing his other claim about inheriting Fain's caseload after Fain retired (surely those cases would have been divided up among all agents = but only until Fain was replaced.
There was foot-dragging in the Oswald cases for reasons other than a "large" caseload.