Lexington PD

Early on in hiring process, not a regular user but if I smoked a joint but not sure if it's been a full year (if not it's close) what are the odds of getting DQ'd. I'm going to be 100% truthful. Never done any other drugs before in my life. I don't want to fail the polygraph because I truly don't know if it has been a full year. Anything will help thanks.