Typically, truth-tellers report more detailed statements when interviewed immediately, compared to after delays (displaying forgetting), whereas liars report statements containing similar amounts of detail when interviewed immediately or after a delay (displaying a metacognitive error). Accordingly, the diagnostic utility of the ‘richness-of-detail’ cue is reduced after delays. We investigated if initial interviewing can facilitate lie-detection using the richness-of-detail cue in sub-optimal memorial conditions, that is, when (i) interviewing occurred after a three-week delay and (ii) truth-teller's attention during encoding was manipulated. Participants (n = 152) witnessed an interaction, that was meaningful to (and intentionally encoded by) liars (n = 50) and half of truth-tellers (n = 51), but meaningless (and incidentally encoded by) the remaining truth-tellers (n = 51). Participants were interviewed after three weeks. Half of the intentional liars and half of the intentional and incidental truth-tellers were also interviewed immediately (initial interview-present condition), whereas the remaining participants received no immediate interview (initial interview-absent condition). Results showed intentional and incidental truth-tellers reported after three weeks more detail in the initial interview-present (versus absent) condition, whereas intentional liars' statements were unaffected by initial interviewing condition. After three weeks, more intentional liars and intentional truth-tellers were correctly distinguished in the initial interview-present (versus absent) condition.