The Pattern or Practice probe will determine if the department engages in unconstitutional or unlawful policing.
On August 5, Attorney General Merrick Garland said his team will examine whether the department uses excessive force, retaliates against protesters, discriminates against minorities, or violates the rights of individuals experiencing homelessness or a mental crisis.
Hours after the DOJ announcement, Phoenix Police Chief Jeri Williams said, "We embrace it, we welcome it."
Experts though are quick to point out that no chief really wants the federal government to launch lengthy investigations aimed at finding flaws and failures within the department.
"It's going to be painful,” said Dr. Jeff Hynes, a retired Phoenix police commander and current Justice professor at Glendale Community College. “But part of the painful aspect of this journey will be the improvement for our community, our city, our state, and the nation as a whole.”
The process will be long and public, as the DOJ is already soliciting community voices who have been impacted by Phoenix police.
"They're going to do ride-alongs, they're going to do community meetings, they're going to examine all aspects of the police department," said Dr. Hynes. "There's going to be some apprehension and there's going to be some fear [among officers]... But this examination is going to improve us."
"I would say the range is probably a minimum of one year," said Arizona State University Professor Michael Scott. "Some of these have stretched on for 10, 15, almost 20 years."
The investigations are not launched lightly.
"The DOJ simply doesn't have the time and resources to go on fishing expeditions," said Scott, who is Director of ASU's Center for Problem-Oriented Policing. "They usually have some reason and evidence to initiate these investigations."
Professor Scott says these "Pattern or Practice" investigations often lead to civil lawsuits or consent decrees aimed at ensuring compliance with the DOJ's recommended reforms. But he also believes the DOJ alone cannot institute major, long-term changes.
"The lawsuits, in and of themselves, are unlikely to realize those results," said Scott. "The city must, ultimately, come to embrace the kinds of policing practices that the reforms are trying to bring about - because it's police administrators that have the greatest amount of influence over how policing is done in any community, far more influence than the US Department of Justice."
Jared Keenan, an attorney with the ACLU of Arizona, shares Scott's assessment of real reform that occurs in a department.
"That's why I'm somewhat less optimistic about the internal culture of the Phoenix police changing or being open to change enough that actual reforms will be implemented," said Keenan. "It's not as if this investigation came out of nowhere. For years, advocates, community organizations, and reformers had been speaking out about the abuses that they and their communities are facing at the hands of the Phoenix Police Department."
Professor Scott said the DOJ involvement may help the more reform-oriented Chief Williams advocate for changes that in normal times would have received major push back internally.
"Police chief's in Los Angeles, Pittsburgh, Cincinnati, and other major cities have publicly said that the Pattern and Practice lawsuit, provided the legal push [and] clout to get some changes made that were difficult for the chief to make by him or herself."
"This gives us the opportunity to shine and to examine these issues that we've had for decades," said Dr. Hynes.