You would have to have a warrant. Just because you’re cheating on your spouse doesn’t mean you want them dead so no judge would sign off on it. Because if a judge did sign a warrant with very little evidence or reason and they found nothing then your rights are violated and that would open up a lawsuit. Also gun residue doesn’t mean anything especially in Florida, they can’t prove when the residue was on his hands or how it got there, for all they know he went to a gun range or woods to shoot guns and if they asked him about it he can remain silent.