If you are abroad in a spanish speaking country and unfortunately you get into trouble and need to talk to a lawyer you must say:
-'Quiero hablar con un abogado'.
(I want to talk to a lawyer)
or ask:
-'Puedo hablar con mi abogado?'
(can I talk to my lawyer?)
Other sentences regarding an arrest are:
-Estoy arrestado/a (Am I under arrest?)
-No he hecho nada malo (I haven't done anything wrong)
-Puedo pagar la multa ahora? (Can I pay the fine now?)