If the police/FBI are so sure about Uncle Charley's guilt, or if they even have a strong suspicion, they would be in their rights to bring him in for questioning and to have his damn photo taken for I.D. purposes, and all this chicanery would be avoided.
Well, we know that that one detective had a thing for young Charlie. Maybe his wanting to get into the house to interview the family had more to do with meeting young Charlie than apprehending old Charlie. You think?
Devils Advocate: Maybe they didn't wanna spook him until they had a solid case. Bringing him in for questioning/printing/photographing and then some high $ lawyer getting him out from a temp holding cell might have been something they wanted to avoid. If they got his photo surreptitiously and a grand jury ran with it, it would have given a Judge enough to withhold bail.
IMHO, the flaw was Uncle Charlie anticipating that Charlie would go out to the garage, alone no less, so he could asphyxiate her ... lame, lame, lame. And I love this film !! I just try to not think about it ...
What makes even less sense is that Uncle Charlie would freak out about that article in the newspaper. Why would he think anyone in the family would think the story was about him? If there was a photo of him, yeah, but otherwise it just made no sense.
Thanks everyone, I like this film too, but the plot is weak in a few places. The fact that there are,conveniently, two suspects under investigation, and just because the other one ran and gets killed, Uncle Charlie is off the hook ? The other one is: how in the world would the niece explain her uncle's death on the train in a satisfactory and realistic manner without admitting the truth ? He just "accidentally fell off the train...??". Good movie though...
Rather than reply to the OP who isn't even here, I'll reply to someone who is.
The OP said,"If the police/FBI are so sure about Uncle Charley's guilt, or if they even have a strong suspicion, they would be in their rights to bring him in for questioning and to have his damn photo taken for I.D. purposes, and all this chicanery would be avoided. "
At the beginning of the film, I assume that the FBI actually were trying to bring him in for questioning. Charlie was dodging them. He kept slipping through their fingers by staying just one step ahead of them. He gave them the brush by leaving town and staying with his sister's family.
By dodging them, he just made the investigators that much more suspicious.
Anyway, that's how I saw it.
This was my impression also. The FBI weren't able to catch-up with Charlie yet. They suspected him but he kept dodging them and they could finally set the trap to catch him when he arrived at his sister's home.