What do you mean by offline wallet? The only times I've heard of offline wallets is in the context of preventing your bitcoins from being stolen, not of avoiding being caught by police.
You can generate a wallet on a computer that isn't connected to the internet and then get someone to send money to it. A wallet is just a bunch of fancy cryptographic tools, none of which need to be online. Once you are ready to spend your Bitcoins, then you'll need to communicate with the blockchain, but not before.
