Doing a report and can't get a definitive answer. if someone took oxycodone that was over 5 years old would it still work? if yes, would it work just as well as it originally did?

I doubt it: The FDA requires any drug maker to have a "use by" or expiration date for any monitored product. That is the last date the drug company can assure it retains potency at the prescribed dose. After that date the potency (strength) can decline over time. The speed of decline varies with the drug and the way it is stored. Work is a relative idea. Thirty % of people think a sugar pill works.