[atakan_gurkan]

Not necessarily. Unless the presence of the accusation already was used to get that 30% number, you also need to take into account the a priori probability of someone maliciously lying (or better yet, the particular accuser to be lying in this case) and apply Bayes's theorem.

[mbg721]

I should have expected Simpson's Paradox here. Nevertheless, I think the possibility of witch-hunting is high.