While your metaphor is merely intended as a comparison of aiding a crime, it's made hazier by the introduction of a crime of a grisly nature (murder) committed

While your metaphor is merely intended as a comparison of aiding a crime, it's made hazier by the introduction of a crime of a grisly nature (murder) committed directly (the source pulls the trigger; it is not a murder caused by a third party without the knowledge of the source and the journalist) A better comparison would be a journalist buying a wrench that can pry open a certain box, or conversely, a lock that makes it very hard to open a certain box.