I saw that several times in the US practicing law; the District Attorneys were formidable opponents, but the second any contradiction in their case became evident, they would fold their case like a busted Blackjack hand. I think it was called legal ethics.
One time it was something as simple as a contradiction concerning which police officer had given the breath test to a drunk driving suspect; they asked for a break, than came back and asked the court to dismiss the case.