It depends on exactly what you did. There is no statute of limitation for murder.
Cal Penal Code 401. Every person who deliberately aids, or advises, or encourages
another to commit suicide, is guilty of a felony.
§ 401 has a 3 year statute of limitation, see http://law.findlaw.com/state-laws/criminal
Please tell me your location and I will look for a local criminal defense attorney who offers a free consultation to discuss this with you.
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However, you can ask me hypothetical questions.
Assisting someone to die can cover a lot of different conduct. Allowing a terminal patient to die is different than doing something that causes death.