How to send a confidential file over the internet to my lawyer?
If you have secure (enough) phone contact with him/her, you can deter hackers by putting the file into a password-protected ZIP/RAR and teling your lawyer the password. If you really want to make it next to impossible for a hacker to get the file, you can get into TrueCrypt, but if you're not paranoid about it, a passworded ZIP should be fine.
The easiest way is TitanFile.com You can send and receive confidential information, get receipt notification and verify identity of recipient before giving them access to the files. There is a free plan I believe.