I never really used it, but when I was reading up on the feature, the hidden partition was inside the decoy partition. The decoy partition would actually overwrite your secret partition if you filled it up. They couldn't even see if there was a secret partition or as even the free space was full of random noise or encrypted data. Granted this would work much better when your hidden data is very small compared to the decoy data, and I'm guessing that if guilty, this guys hidden data would take up a sizable space.TrueCrypt had that option. The only problem was that it's pretty obvious that there's something there when the volume size and the disk size don't match up at all. Between that and the secret volume being advertised as a feature, it wasn't exactly clever.