Due to this, they have requested his cousin to hand over information related to his Google AdWords account.
I find this very hard to believe to be a real email from Google. Typically legal subpoenas are sent via signature request mail. Also, they would never request your account information - they already have access to that.
So beware of these unusual phising attempts.
Forum discussion at WebmasterWorld.
Wow, this is actually a real email! I cannot believe that this can be possible. Eric Goldman reported the details and I have my personal thoughts at SEL with Google Keyword Legal Subpoena Has Major Competitive Concerns.