An expert in death-penalty defense rightly calls it "a big deal" that starting next year, Police Commissioner Charles H. Ramsey will require video recording of all interrogations in homicide cases. The practice - already followed in police departments across the country, including Ramsey's former force in Washington - will make Philadelphia's justice system more just.

Video recording will guard against mistreatment of suspects and witnesses. It will help assure that police and prosecutors arrest and charge the right people, minimizing the risk of false, coerced confessions. And it will prevent suspects from wrongly alleging police impropriety by allowing judges and juries to hit the rewind button and see for themselves.

Along with related moves to prevent excessive detention of suspects and eliminate errors in suspect identification from photo lineups, the recording policy is welcome and overdue. Marc Bookman, director of the Philadelphia-based Atlantic Center for Capital Representation, explained why the change is such a big deal: "People have been admitting to things they haven't done for as long as they've been committing crimes. ... DNA exonerations over the past 24 years have established not only how error-prone our system of justice is, but how more than a quarter of those wrongly convicted have been inculpated by their own words."

In one case that fell apart recently, Nafis Pinkney claimed he had been coerced into confessing to a 2009 double murder in the city's Cobbs Creek section. In October, after four years in jail, he was acquitted and set free. In another 2009 case, Unique Drayton was charged with killing her roommate in Overbrook, but she had confessed only after 41 hours in police custody. A judge threw out the confession.

In light of such cases, as well as recent corruption allegations involving a homicide detective, this step to bolster public confidence in the most critical police investigations should be hailed and eventually expanded.

It's a positive sign that the initiative is being undertaken not in response to a lawsuit, but as a result of concerted discussions among police, noted local civil rights lawyers David Rudovsky and Dennis J. Cogan, and the Pennsylvania Innocence Project's Marissa B. Bluestine.

For the city's investigators, the new procedures will no doubt take some adjustment. And Ramsey will have to monitor compliance closely given the department's historical resistance to change. But it has been years since the commissioner inaugurated video recording of interrogations in Washington, and there's no doubt the policy is right for Philadelphia, too.