Does this mean they dont want to help the speaker or more along the lines of a general statement stating the police arent bad guys?
If you put the stress on dig, it could mean that they want to help only you, no one else. But that's certainly not the first interpretation that would come to mind when reading this sentence.
It's not really a likely enough phrase - plus, if it were, the "only" would be more idiomatic after the verb.
Wouldn't it be "the police wantS to help you" as it is a 3rd person sentence?