A French film from a couple of years ago: a teenage girl is raped and murdered and her grieving father broods violently over taking matters into his own hands once he finds the culprit. Soon a suspect is arrested and the father seems content to let justice take its course. The suspect, however, begins to write to the father, explaining that he is not the person responsible for the crime and has been wrongfully accused and incarcerated. Initially the father sees these letters as a ruse; yet in time he empathizes with the prisoner and by the end of the film actually requests his acquittal. The prisoner is indeed acquitted, but another turn of events leads to a shocking conclusion.

Counter Investigation (http://www.focusonfrenchcinema.com/2008/film_ContreEnquete.htm)