Because anyone who used a Blackberry would realize that it is far easier to keep a record of Blackberry communications than ordinary cell conversations, so there’s no reason this would be more of an issue because he has a Blackberry.
I apologize for mis-reading your post. I read your insinuation as a belief that it would be difficult to maintain such a record.
Still, I don’t know why you had to sneer at the other poster that obviously he or she never has had a Blackberry...