Any good DA can and will prosecute the scum... some just choose not to do so. No, they may not win the case, but they can charge them with a crime and bring them before a jury.
Scott Peterson was found guilty on circumstantial evidence...because a DA charged him with a crime.
Well, able and willing are two different matters. This guy has walked in Illinois, Missouri and now Arkansas, although we are hoping that after having done their investigative work for them, maybe the history will give our prosecutor the incentive. I'm not holding my breath though. He seems to have a soft spot for pedophiles.