ABC News' '20/20' Reports on Ankle Bracelet-Monitoring Failures and Murders Committed by People Ordered to Wear Them 5/25

This Friday, "20/20" will report on a nationwide investigation that found at least 50 murders allegedly committed since 2012 by people who at the time were under orders to wear electronically monitored ankle bracelets. In some cases, authorities failed to appropriately monitor people wearing ankle bracelets or to respond to alerts set off by the electronic devices. The program features interviews with Rafael Zaldivar, the father of a young man who was killed in Orange County, Florida, by someone wearing a device; and Bill Cregg, who was the first to arrive on the scene of a murder in Syracuse, New York, by a man who had removed his device. In both cases the devices triggered alerts before the murders were committed, but authorities took no action. "20/20" airs on Friday, May 25 (10:01-11:00 p.m. EDT), on ABC.

An estimated 300,000 people are currently wearing ankle bracelets for a variety of reasons, including some for alcohol monitoring. Proponents say the systems enhance public safety, reduce prison costs and provide social benefits.

In the Florida murder, a man named Bessman Okafor broke into the home of roommates Brienna and Remington Campos and Alex Zaldivar, shooting all three and killing Alex. Okafor was wearing an ankle bracelet after being charged with a robbery at that home earlier in the year. Two of the roommates were scheduled to testify against him the following day in connection with that crime.

In the Syracuse case, "20/20" details the murder of Lori Bresnahan by David Renz, who was supposed to be wearing an ankle bracelet while awaiting trial for possession of violent child pornography.

ABC News' Brian Ross investigates the crimes and the failure of ankle bracelet-monitoring to prevent them.

"20/20" is anchored by Elizabeth Vargas and David Muir. David Sloan is senior executive producer.