What is the ruling on submitting a memorandum requesting the release of a premeditated murderer based on a general amnesty, and what is the ruling on the fees earned from this case?

This person's situation is one of two:

First: He may have been unjustly convicted, and his innocence is certain. In this case, there is no harm in striving to remove the injustice from him, and it is permissible to take money for doing so.

Second: He may have committed this act and was convicted based on that. In this case, it is not permissible to strive to acquit him, let alone take money for it, because the obligatory ruling for him is qisas (retaliation in kind) unless the next of kin pardon him.