What’s the worst that can happen if you get arrested for DUI and talk to the police without an attorney?

http://www.bbc.co.uk/blogs/adamcurtis/entries/3662a707-0af9-3149-963f-47bea720b460

“In August 1971 an ordinary London policeman arrested a man who was driving drunkenly down Tottenham Court Road. He turned out to be Oleg Lyalin who was a KGB agent. […] Lyalin panicked and offered to tell MI5 the names of all the Russian spies in Britain. […] the Home Secretary expelled 105 other members of the trade delegation because Lyalin said they were spies.”