Can the DA use prior arrests as evidence against me? I have never been convicted of any charges in the past, but the DA says those past arrests prove that I'm guilty, on my current charge.
You're talking to the DA without a lawyer? There is probably nothing else that you could do that is more likely to land you in prison than that misstep. A case involving prior acts is complex, and you need a very skilled lawyer and needed to have hired him a long time ago.
The DA cannot use prior arrests in his case in chief, but may be able to use prior arrests in rebuttal, especially IF you take the stand and open the door. See website for info on retaining the right attorney: http://www.lawrencelewispc.com/pages.php?go=pinfo&PID=38
Good luck