A sentinel event could be the conviction of a person later proven to be innocent of the charged crime, a police-citizen encounter that unexpectedly turned violent, the release from prison of a dangerous person, or even a “near miss” that could have had a disastrous effect. A sentinel event review is not so much interested in assigning blame for the event to an individual or agency, but rather in examining the underlying factors that contributed to the event and developing a reform strategy that can be implemented and tested to determine whether corrective measures have succeeded in addressing causative factors. To date, NIJ has achieved a number of significant milestones in the SEI. First, NIJ brought together criminal justice experts and potential early adopters to vet the SEI concept . Second, it published “Mending Justice: Sentinel Event Reviews,” a special report that discuses the background of the SER concept, with commentaries from the Attorney General and 16 respected criminal justice practitioners and researchers. Third, in 2014 and 2015, NIJ funded four research projects that examined whether the SER concept can be implemented and the best ways to bring SERs into the justice system. Web access is provided to reports on each of these four projects.