Bleg: Augustine and Inherited Guilt

I'm curious about what the textual basis is for attributing the doctrine of inherited guilt to Augustine. It's easy enough, actually, to find passages in English translation that sound like it, but I find it difficult to match them with anything suggestive of inherited guilt in the Latin. For instance, the words usually translated as 'guilt' -- reus, reatus, obnoxia -- don't fit the English word 'guilt' very well. Obnoxia and its cognates seem to fit it poorly indeed; a better translation would usually be 'subjection' (cf. Hebrews 2:15, which in the Vulgate is, et liberaret eos qui timore mortis per totam vitam obnoxii erant servituti). And a number of apparently incriminating passages turn out just to mean this: that we are united in a bond of subjection that we receive from those who came before. Reus and reatus are much closer, but they also seem to be weaker than the English term 'guilt', since in general they tend to mean simply liability for a debt or penalty, and liability does not [or rather, need not--ed.] imply culpability, whereas 'guilt' does ('guilt' usually suggests fault). But I'm not an Augustine scholar by any means, and Augustine's Latin regularly wipes the floor with me, so it could very well be that I'm simply missing something key. So does anyone know what the basis in the original texts is? And what's the reason we don't call it 'inherited liability' or 'inherited subjection', given that these, at least at first glance, look like more reasonable labels?