Wildlife must be removed or released from traps daily; except for colony and killing-type traps, which must be checked every 48 hours.
Here's an exert from the Missouri trapping regulations, it's very plain to see that not only morally but from a legal aspect the trapper is in violation of running a trap line.
As for killing the dog, if the trapper had done so, the trapper would have been in violation of Missouri law.
You can not kill a dog in Missouri for just being on your property in traps or other wise.
As for releasing the dog from the traps without getting bit, thats not that hard to do.
A cover garment of some kind thrown over the dog and wrapping the dogs head will keep the dog from biting you.
Glad to here the dog was released from the traps and the wife and dog is doing fine.