False witnesses of God (pseudomarture tou qeou). Late word, but pseudomarturew, to bear false witness, old and common. The genitive (tou qeou) can be either subjective (in God's service) or objective (concerning God). Either makes good sense. Because we witnessed of God (oti emarturhsamen kata tou qeou). Vulgate has adversus Deum. This is the more natural way to take kata and genitive, against God not as equal to peri (concerning). He would indeed make God play false in that case, if so be that the dead are not raised (eiper ara nekroi ouk egeirontai). Condition of first class, assumed as true. Note both per intensive particle indeed and ara inferential particle therefore.