This Aspiration adds the ability to live two separate lives. A public life as a good person and a dark secret life that will end in murder.
In CAS give your Sim the Secret Life Aspiration and trait. You’ll also need the Duplicitous Trait to access the needed social interactions.
There are 3 social menus you can use. Public Persona, Risky Behavior, and Dark Secrets. To access Dark Secrets you’ll need to self click on your Sim and select “Smoke Crystal Meth”. The Kill Sim interaction will appear also but it’s meant for use on other Sims. Kill Sim will show up on other Sims as a single interaction.