I Found Used Syringe And Needle In My Sons Apartment,

i found used syringe and needle in my sons apartment, he sais is for insulin, but he is not diabetic,but he used some steroids for bodybuilding last year, nd also he is drug addict in recovery, there is no color at all in syringe, looks clear, syringe is small with short thin needle and orange cap, where can i take it to identify liquid used in it?