Composting is a specific set of chemical processes that take place in a hot, highly oxygenated environment with the proper mix of nutrients for microbial growth. It is not comparable to ordinary decomposition in soil.
Composting can destroy prions, but it might be different to ensure you’ve destroyed all of them. Read more here: https://www.beefresearch.ca/fact-sheets/can-composting-destroy-bse-prions/
PS: I think it’s not good to joke about killing people, even shitty people.