The condition of mutual consent is crucial not just to the research, but also to the aim of its generalizability. The operational basis of holding such conferences at all depends upon consent, since RJCs without consent are arguably unethical. The Review’s conclusions are appropriately limited to the kinds of cases in which RJCs would be ethical and appropriate.
Among the kinds of cases in which both offenders and victims are willing to meet, RJCs seem likely to reduce frequency and (with less data) costs of future crime.
Read the whole article and note in particular their definition of a restorative justice conference.