If we can't get them to get help, why should we believe that an interventionist (a "stranger") could do any better?

The most obvious answer is that because you are family, you are already working at a severe disadvantage. The person already has habits with the family, ways of controlling people. He knows what buttons to push. He knows everyone's history, whose sheets to pull and how to manipulate the group through crisis.

An interventionist has an exterior vantage point that the family has long since lost. As a result, the interventionist can get the family onto a game plan, taking into consideration each person's individual truth . While a family, working within its own confines, often just argues about whose plan is best, or will end up executing plans of their own without informing anyone.

Also, people have an emotional history with other family members, and so they will get off course and not give it another thought. With an interventionist, you have someone who's your point person, keeping the goal and the strategy alive, working and in plain view, no matter how muddy the water may get.

An interventionist should also be someone who has experience with addiction, ideally. My best recommendation is not to hire a therapist or a doctor or a psychiatrist who thinks he knows how to do an intervention because he has read a book on it somewhere or has “done some interventions.” Always get references! The ideal candidate is someone who's actually been there, and can talk to the person from personal experience. This is what reaches the addict, and this is why I succeed, time after time. Not because of the books I've read or the certifications I have, but because I have an intimate history with just about every drug, over many years of use, and in many different circumstances.

A lot of families keep coming up with new conversations to throw at the addict, believing that this new conversation will be different: if we do this it will be different, if we say this meaningful sentence, this profound phrase, if we bring his attention to this consequence, that the addict will have the correct realization at last, see the error of his ways and will go into treatment. That, sadly enough, is what families get locked into, doing it over and over. Same endeavor, different script, same results.

If you are considering hiring an interventionist, then my advice is this: don't experiment on your own, stabbing in the dark with last-ditch efforts, and then when everything is totally screwed up, in chaos or worse, you call the interventionist. An interventionist can work best when he can put as many of his cards on the table as possible. You don't want to undermine everything the interventionist is truly capable of doing by playing the cards before he can play them as part of a larger strategy. Let the interventionist play the cards from the start. Let him orchestrate things.