I think I see a very obvious problem with this: in the experiment they ran, the interviewer seems to be leading the interviewee in how to remember an episode. Which means there is no way to make sure the interviewer is not (consciously or not) planting those very same "rich details" that purportedly make the difference between a lie and a truth, into the interviewee's narration.
So I don't see that they're avoiding a "Clever Hans" situation at all. They could be leading their interviewees on, providing subtle clues to the ones that are telling the truth, but not to the ones that are lying.
And even if this was double-blinded, there's still no way to ensure the interviewer doesn't interact in a different way with different interviewees, therefore messing up the results of any experiment pretty badly.
So I don't see that they're avoiding a "Clever Hans" situation at all. They could be leading their interviewees on, providing subtle clues to the ones that are telling the truth, but not to the ones that are lying.
And even if this was double-blinded, there's still no way to ensure the interviewer doesn't interact in a different way with different interviewees, therefore messing up the results of any experiment pretty badly.