deals are fine so long as it’s not immunity. Give him 1/4 off sentence or some thing. This immunity deal stuff in any case is never a good thing.
because telling the truth in situations such as crime should not have to be rewarded in a decent society. And I think if people come forward and tell truth they should get lesser sentence, than caught soon and tell truth immediately, but those who are caught a while after the crime and take a while to finally “crack” or make deal - should get very little leniency on sentence. They cost the society much in terms of man hours in investigating etc and also likely did more damage in ways to more people during the extra time before caught.
we should not reward evil/bad intent.