When DV8 blackmails Ada on the bridge by threatening to expose Ada for the car explosion several episodes earlier, she should know he is bluffing. 1) the call was untraceable (as Ada had requested), so DV8 has no direct evidence pointing to Ada. And 2), his only way of exposing Ada is to expose himself as well, since he was the one who made the phone call triggering the explosion (which he even admits when he is making his blackmail demand).