I was just charged with petit theft at walmart due to not being familiar with the self check-out and the arresting officer lied on report??

My best legal advice is to exercise your right to remain silent.  In my legal opinion, after numerous years of practicing criminal defense law, I firmly believe a defendant can NEVER help him/herself by talking to law enforcement.  When you disclose to the law enforcement officer or the store's security person any information or idea about why you think they are wrong, you are simply giving them an opportunity to try to fix any potential weaknesses or oversights.  Why would you want to help them improve their case?     My next best legal advice is to get an attorney to represent you.  If you cannot afford one, you are entitled to have a court-appointed attorney represent you.  Many court-appointed attorneys are very good.  But if you can afford an attorney, ethically you should do so instead of trying to get a court-appointed attorney.     Once you have an attorney, discuss the issues you believe exist (e.g., what do the officer's and store cameras/videos record).  Your attorney should be able to determine how much to discose from a strategic standpoint and how much must be disclosed from a legal standpoint.