Three years ago, Philadelphia’s criminal justice leadership — the courts, district attorney, public defender, mayor and others — came together around a bold plan to turn a few million dollars in grant funding from the MacArthur Foundation’s Safety and Justice Challenge into an unprecedented collaboration that would transform the city’s justice system and cut the jail population by 34 percent.

Today, the jail population is just over half what it was in 2015. The dilapidated and despised, 90-year-old House of Correction stands empty. And people finally can be released with electronic monitoring even if they don’t have landline telephones.

But other planned reforms never materialized — in particular, an algorithmic tool meant to help determine whether to release individuals awaiting trial. Now, it seems the collaboration has broken down as well.

The district attorney and chief public defender have written an excoriating letter to First Judicial District leadership officially withdrawing support for the Risk Assessment Tool — referred to in the letter as “the RAT” — accusing the court of refusing to share information about the tool, alleging the courts misrepresented their position to the foundation, and raising questions about the fact that the tool was under development for years before the collaboration sought $100,000 of MacArthur funding for it.

“Increasingly, we question whether this has been an excuse for the failure to move forward to end cash bail, as promised," reads the May 3 letter, obtained by The Inquirer and signed by District Attorney Larry Krasner and Keir Bradford-Grey of the Defender Association of Philadelphia. "These concerns are bolstered by the fact that the ‘robust alternatives to cash bail’ promised in the MacArthur grant applications have never materialized.”

Critics say such algorithmic tools can end up reflecting racial disparities embedded in the justice system — and the district attorney and defender say the court system’s lack of transparency compounds that worry.

Mike Dunn, a spokesperson for Mayor Jim Kenney, said the mayor was “disappointed” by the letter, as the administration had hoped all parties could collaborate to develop a tool that would resolve legitimate concerns.

“The move is particularly perplexing, given that both agreed to support the effort as part of the city’s application last fall for additional funding through the MacArthur Foundation Safety and Justice Challenge,” he said in a statement.

Ending cash bail has been a shared goal of the collaborators, partly in response to a growing body of research that bail contributes to racial disparities in the justice system. White defendants in Philadelphia are twice as likely as black ones to go free until trial, which in turn leads to fewer convictions and shorter sentences.

Moreover, the Philadelphia court is battling a lawsuit over its bail hearing process filed by the ACLU of Pennsylvania, which asked the state Supreme Court to compel change. The hearings, held by video, often last just a few minutes, during which defendants do not get to confer with a lawyer and are typically warned not to speak. According to the ACLU, magistrates often impose money bail without considering ability to pay.

City and court leaders have emphasized that no major jurisdiction has eliminated the use of money bail without a risk tool. Such tools are in use in New Jersey and Washington, D.C., which have led on bail reform.

But over the past year, civil rights groups, justice reform advocates, and even a consortium of the nation’s largest technology companies have expressed concern about the use of the tools.

In March, the Defender Association proposed an alternative way to end reliance on money bail.

The proposal, developed at the request of court leadership, would eliminate bail hearings for most defendants charged with misdemeanors; they would be released with a summons to appear in court. Those held on more serious charges would undergo a preliminary arraignment hearing to consider whether they can be released outright, or with some supervision. Only in cases where the defendant is a flight risk or a perceived danger to the community would the district attorney file a detention motion — which would result in a release-determination hearing where a judge could decide to detain the defendant or impose bail.

According to the letter, court leadership did not respond to that proposal: “Instead, on April 10th, [pretrial chief] Michael Bouchard told MacArthur board members that the [court] was continuing to move forward in building the RAT and that all other stakeholders had agreed to join in those efforts. This declaration was a misrepresentation of our positions."

A judicial district spokesperson did not immediately respond to a request for comment on the letter, or on why the tool has been under development for at least seven years but has never been implemented. The district attorney and chief defender also declined to comment.

A 2013 annual report by the First Judicial District notes that “the new risk assessment tool is being developed by Professor Richard Berk of the University of Pennsylvania using sophisticated data mining techniques and is near completion.” Berk is the developer in charge of the tool under development today.

In an interview, Berk said he had completed "six or seven” iterations of a tool for pretrial decision-making in Philadelphia over the seven years. He said he has never received payment from the city for that work.

“You have seen the political gridlock over there, and, until they resolve that, nothing is going to happen," he said.

He said he believes his mistake was focusing on “objective fairness.” Now, he said, he’ll prioritize “political acceptability” as well. He said his latest version of risk assessment does so by only inputting data from white defendants.

“The result is more equitable," he said, but "could be making everyone equally worse off. I’m throwing out two-thirds of my data. It’s not as accurate, but it’s equally inaccurate for everyone.”