Ask an LN and they will tell you there was nothing wrong with Day lifting a print and not telling anybody about it for several days.
This is one of these things (on a very long list) that, when looked at it with an open mind, raises massive questions about the entire LN narrative.
It's not just Day lifting a print, it's the importance of the print.
By the evening of the assassination Day had evidence that Oswald had handled the murder weapon!
By the time Day lifted the print he already had Oswald's palm print to for comparison. What priority could there be above this evidence?
What greater piece of evidence exists that ties Oswald to the murder weapon? That directly implicates him in the assassination of JFK?
There is none.
Mr. Belin: At the time you had this did you have any comparison fingerprints to make with the actual prints of Lee Harvey Oswald?
Mr. Day: Yes, sir; we had sets in Captain Fritz' office. Oswald was in his custody, we had made palmprints and fingerprints of him.So, why didn't Day release this fundamentally important piece of evidence to the FBI?
Mr. Belin: Is there any particular reason why this was not released on the 22d?
Mr. Day: The gun was being sent in to them for process of prints. Actually I thought the print on the gun was their best bet, still remained on there, and, too, there was another print, I thought possibly under the wood part up near the trigger housing.
Mr. Belin: You mean the remaining traces of the powder you had when you got the lift, Exhibit 637 [palm print], is that what you mean by the lift of the remaining print on the gun?
Mr. Day: Yes, sir. Actually it was dried ridges on there. There were traces of ridges still on the gun barrel.
He is saying he didn't send his lift because he felt confident there was enough of a print left behind for the FBI to make an identification.
Does that make sense to anyone? He kept the most complete print and sent the FBI whatever was left on the barrel?
And, as we know, by the time it got to Latona this mysterious print had vanished as if it had never been there at all.
Does that make sense to anyone? It was so stubbornly fixed on the barrel cellophane couldn't remove it but it then, somehow, vanished so completely that there was not the tiniest part of it left.
One has to assume that his top priority would then be to establish whether the print he had lifted matched the one they had taken from Oswald. Establish the all important proof that Oswald had indeed handled the murder weapon. The one piece of evidence that would truly nail him:
Mr. Mccloy: How about the palmprint?
Mr. Day: The palmprint again that I lifted appeared to be his right palm, but I didn't get to work enough on that to fully satisfy myself it was his palm. With a little more work I would have come up with the identification there.
What does he mean "I didn't get to work enough on that"?
He had the print for days.
He had the best evidence that Oswald was the killer in his hands. What else was he working on that was more important than this?
There was no print on the underside of the barrel.
That's why there was no trace of it when Latona examined the rifle.
That's why Day never had enough time to work on it.
OR
Somebody wiped the barrel clean before Latona received it.
Day spent days trying to make the match but couldn't manage it.