Some evenings I spend with my Father, he uses Veritaserum on me and I am learning to block it. We are increasing the doses each time and it is rare that I let a secret slip. It did create a lot of awkward moments in the beginning. I was an open book for him, even a drop made me spill a truth. I can hold up to over a teaspoon, without spilling a secret or even feel the urge. I am already over the Ministry limit for interrogation, but someone like the Dark Lord would never hold to that standard. That is why I am pushing myself. Each time I take a higher dose it is awful, I sweat, have to bite my tongue until it bleeds and focus on a lot of other memories until the effects start to fade away after half an hour.