So I’m re-watching old episodes of a certain series (please don’t name it even if you figure it out, to avoid any spoilage) and at one point of the plot a character tries to frame another by knocking him unconscious before putting his fingerprints all over a murder weapon.
Here’s where it gets tricky : rather than, say, dropping the weapon on a street or in a dumpster for someone to find, he decides to drop it off a shallow pier because he knows there’s a diving class there early in the morning.
But would fingerprints actually stay on a knife or gun handle overnight, if dropped in an ocean ? From what I understand fingerprints are a residue of bodily oils, don’t they simply dissolve in water, particularly water that isn’t still ?
Oil is not generally soluble in water, which is why you need a detergent to clean anything greasy.
Having said that, water can shift oil, especially moving water. So I guess it depends on how adherent the oil in the fingerprints is, how much the water is moving, how warm it is, and a host of other factors. I don’t know whether, in practice, there is much success in recovering fingerprints from objects that have been thrown into bodies of water.
I watch a fair amount of American and British TV shows which make significant use of forensics. It is pretty obvious that much of what these people do is entirely fictional, with little regard to what’s actually possible.
What, isn’t the instruction for obtaining a fingerprint “Press firmly” ?
And isn’t the grip loose just before it becomes non-existent ?
Ok I get it… there is the process with a firm grip in the palm, any contact with the finger tips smooth surfaces is likely to be brushed …
And with the gun the palm print is on the friction enhanced surface… rough surface.
However thats not relevant to the OP’s case, as in that case the fingerprints were being put there on purpose.
The weapon is more likely to have a identifiable traces on it … eg fibers, hair, plant material.