This is a journalism question, and an interesting one. A quick and glib answer is that you should not lie to hostile sources because you are not the police and this is not a criminal matter. Police are dealing in an entirely different theater of motivations, risks, and consequences. They are dealing, oftentimes, with desperate, evil people.
We, presumably, are not. We are dealing with people who have every right not to talk to us. More important, we are dealing with people who agree to speak to us voluntarily, at their own risk, with an implicit trust that we will not betray them. They have the right to expect honesty and straightforwardness.
Even within this general framework, though, there are nuances. Complications.
This matter of implied honesty was the basis for Janet Malcolm's 1980s New Yorker essay, "The Journalist and the Murderer," in which she famously contended that all journalists are, basically, con men.
The thesis of her piece was contained in its first sentence: "Every journalist who is not too stupid or too full of himself to notice what is going on knows that what he does is morally indefensible."
Her point was that journalists use people -- that we subtly mislead them, flatter them, etc. -- to get what we want out of them. The case around which she built her argument was "Fatal Vision," a book by Joe McGinniss about Dr. Jeffrey MacDonald, who was convicted of killing his family. Malcolm contended that McGinniss had dealt dishonestly with MacDonald to keep his trust and cooperation; she cited the fact that McGinniss didn't tell MacDonald when he came to believe he was guilty -- that he kept stringing him along, letting him think that the book he was writing would exonerate him.
And that was true. McGinniss did do that. And after Malcolm's essay was published, he took a lot of heat.
But not from me. I knew McGinniss -- had socialized with him once or twice. And I had an opinion on this matter, which I wrote about.
I said that there is a direct or an implied covenant between writer and subject: That each will be truthful with each other: Not necessarily entirely transparent -- no human relationship requires that -- but honest with the other as to anything important. Once that covenant is broken, all deals are off. I believe McGinniss no longer had any obligation to deal forthrightly with McDonald at the point he realized McDonald was lying to him about the very central fact of the book -- his own guilt.
This opinion entered the public debate; McGinniss suddenly publicly adopted it.
Anyway, my sole point here is that ethics are complex and situational. In my opinion.



