What happens to an adult if they are arrested for shoplifting?

Shoplifting is a criminal offense. Accordingly you should have legal representation in this matter. An experienced criminal law attorney might be able to get the charge dismissed on a technicality or at leasr get it reduced. If you are a first-time offender, you will probably be offered "diversion" (or your state's equivalent). This is an alternative sentencing program whereby you will plead guilty to the charge, receive a special probation, and upon its successful completion the charge will be withdrawn and your case dismissed. Diversion, however, is only allowed for a first offense. Therfore, if you get into trouble again, it will not be available for you regarding any subsequent charge. That's why if you get a lawyer who manages to get your case dismissed, you will be eligible for diversion in the future if you should need it.

If you are eligible, a PD (public defender) may be assigned to your case. If so, plead "not guilty" at your court date. If you are not eligible for a PD but money is an issue, see if you qualify for representation by Legal Aid (there are income limits) or see if it can recommend someone to help you. Also, check if there is a law school in the area of where the charges where brought; they typically run free/low cost clinics that handle these type cases. Finally, you can contact the local Bar Association in the applicable county; it may have a list of attorneys who will take your case "pro bono" (for free) or at least for a reduced fee based on your income/circumstances.