A shadowy for-profit company and its nonprofit counterpart provide free services to at least 40 far-left prosecutor offices, raising questions about whether it’s working on behalf of taxpayers or of donors who have essentially bought government. The Wren Collective is a shadowy group that emerged from a Cold War-era initiative aimed at promoting Soviet films in the United States. Its current iteration — funded by a former Enron executive and host of other leftist megadonors — claims that America’s “system of policing and mass incarceration is deeply flawed and intractably racist.” The group has intervened on specific criminal cases, written...