Claudius admits very explicitly that he is guilty. He opens his soliloquy by saying, "O, my offence is rank, it smells to heaven;/
It hath the primal eldest curse upon't,/ A brother's murder!" He understands that his actions are wicked, and he fears that he will not be forgiven for them, because he will always be surrounded by the things that made him want to kill his brother in the first place: his crown and his wife. He cannot be rid of these things, so he is, as he sees it, trapped. He ends the soliloquy full of fear that he may have to pay for his deeds in heaven after his death, and, overcome by the thought, he falls to the ground in prayer for forgiveness.