The present experiment examined how the interaction between senders’ communicative competence, veracity and the medium through which judgments were made affected observers’ accuracy. Stimuli were obtained from a previous study. Observers (N = 220) judged the truthfulness of statements provided by a good truth teller, a good liar, a bad truth teller, and a bad liar presented either via an audio-only, video-only, audio-video, or transcript format. Log-linear analyses showed that the data were best explained via the saturated model, therefore indicating that all the four variables interacted, G2(0) = 0, p = 1, Q2 = 1. Follow-up analyses showed that the good liar and bad liar were best evaluated via the transcript (z = 2.5) and the audio-only medium (z = 3.9), respectively. Both the good truth teller and the bad truth teller were best assessed through the audio-video medium (z = 2.1, good truth teller, z = 3.4, bad truth teller). Results indicated that all the factors interacted and played a joint role on observers’ accuracy. Difficulties and suggestions for choosing the right medium are presented.