Many high-profile instances of police brutality over the past year could have been avoided by addressing law enforcement culture, training, and supervision—and an overhaul of police institutions is crucial to prevent more of those cases, a new study released Thursday concluded.

The Police Executive Research Forum (PERF), a nonprofit policy organization based in Washington, D.C., analyzed a number of cases in which officers used excessive force as a first-resort means of addressing situations and found that, in departments throughout the country, police do not receive adequate training in communication, crisis intervention, and nonviolent deescalation of crises.

Rather, a pervasive culture of aggression and competition encourages officers to react with force, even when suspects are unarmed, which has caused "missed opportunities to ratchet down the encounter, to slow things down, to call in additional resources," PERF executive director Chuck Wexler wrote in a summary of the report, Re-Engineering Training On Police Use of Force (pdf).

"Sometimes there is a feeling of competitiveness about it," he wrote. "If an officer slows a situation down and calls for assistance, there is sometimes a feeling that other responding officers will think, 'What, you couldn’t handle this yourself?'"

Deescalating tension or calling in additional resources, in fact, is often perceived as being "antithetical" to police culture.

Amid the growing prominence of the Black Lives Matter movement, police brutality cases—particularly those that are caught on video, such as the killing of Eric Garner, the arrest of Sandra Bland, or the assault on a group of swimsuit-clad teenagers in McKinney, Texas—have become much harder for departments to ignore. The report found that forces in Seattle, Washington; Las Vegas, Nevada; Leesburg, Virginia; and Oakland, California, among other cities, are overhauling tactical training to focus more on deescalation and "emotional intelligence."

But in outlining those efforts, the study also reveals how far behind the departments were, in some cases lacking seemingly basic fundamentals. For instance, as Las Vegas police chief Kirk Primas explained, "Our sheriff recognized that we had to change, and that included a change in the department’s culture. So we revamped our policies, and we put 'respect for the sanctity of human life' in the first paragraph of our use-of-force policy."

Meanwhile, PERF's study comes soon after Amnesty International released a separate report which found that each of the 50 states has failed to comply with global standards on police use-of-force and engage in "a widespread pattern of racially discriminatory treatment by law enforcement officers and an alarming use of lethal force nationwide."

"Police have a fundamental obligation to protect human life. Deadly force must be reserved as a method of absolute last resort," Steven W. Hawkins, executive director of Amnesty International USA, said at the time. "The fact that absolutely no state laws conform to this standard is deeply disturbing and raises serious human rights concerns."

Still, Wexler concluded that the resurgence of the racial justice movement and the sustained activism against police brutality is turning the tide on police culture.

"The last year has taught us that community oversight in the age of the Internet is a powerful force," Wexler writes. "The public’s demands for increased accountability and transparency will continue to work their will on our 18,000 police departments."