FLAGSTAFF, Ariz. — American Indian leaders who criticized the federal government for years over the way authorities handled major crimes on reservations will soon mark progress with the release of newly tracked statistics from the U.S. Justice Department.

Federal prosecutions of cases from Indian Country increased by 54 percent between fiscal years 2009 and 2012, according to a DOJ report obtained by The Associated Press.

“They’ve taken their responsibility much more seriously than before,” said Brent Leonhard, an attorney with Umatilla tribe in Oregon.

The report scheduled for release later Thursday marks the first look at government investigations and prosecutions on tribal lands. It comes as a result of the 2010 Tribal Law and Order Act, which requires the Justice Department to publicly release such figures.

Justice officials acknowledge that their work is far from done, but they say the numbers demonstrate the government’s commitment to combating violent crime on reservations where rates are higher than the national average.

The report also shows that nearly 6,000 Indian reservation cases were referred to the federal government between calendar years 2011 and 2012. Arizona, home to the nation’s largest American Indian reservation, had the highest number with more than 2,000, followed by South Dakota with nearly 1,000 and Montana with more than 500.

Of the 5,985 cases referred from reservations across the country over the two years, about two-thirds led to convictions, while about one-third were declined for prosecution.

“It shows that we’re walking the talk at the Department of Justice,” said Tim Purdon, U.S. attorney in North Dakota.

Purdon leads a subcommittee that reports to Attorney General Eric Holder on American Indian issues. He said federal officials “want to improve public safety” and added that they are working to “remove those most dangerous predators, the most dangerous criminals from Indian Country.”

The federal government and tribes have concurrent jurisdiction in crimes where the suspect and victim are both American Indian, but federal prosecutions carry much stiffer penalties. Among recent U.S. government prosecutions:

•A man was found guilty of sexually abusing a teenager he met while working as a counselor at a summer camp on the Rocky Boy’s reservation in Montana. He was sentenced to more than three years in prison.

•A woman on the Spirit Lake Reservation in North Dakota was convicted of beating her 4-year-old son with a plastic clothes hanger. She was sentenced to seven years in prison.

•A man was sent to prison for 10 years for kicking the woman who was pregnant with his child on the Navajo Nation in Arizona. The unborn child died after suffering a skull fracture and other injuries.

Federal authorities have “really stepped up trying to improve criminal justice in Indian Country and ensure public safety,” said Leonhard of the Umatilla Tribe’s Office of Legal Counsel.

Still, nearly 2,000 cases were declined for prosecution, a matter for which the DOJ has been criticized in the past.

“There are cases that are legitimately declined, and that is appropriate and expected,” said Leonhard.

The DOJ’s report shows that the matters declined in 2011 and 2012 were mostly because of insufficient evidence. Rates for individual states varied widely — from Montana, where 52 percent of cases were turned down, to Arizona, where 20 percent were declined over the two years.

Federal prosecutors, however, don’t measure their performance in Indian Country by declination statistics. Instead, they point to the relationships they’ve built with tribal police, investigators, prosecutors and community members.

Federal prosecutors also have ventured out to Indian Country more often to discuss ways to combat crime, training police officers to become federally certified and bringing on state-bar certified tribal prosecutors as special assistant U.S. attorneys.

“If anything we get way too caught up in looking at the numbers,” said Patrick Schneider, tribal liaison for the U.S. attorney’s office in Arizona. “Declinations is not a really good number to look at to find out whether we’re doing a good job or not.”

Grant Walker, tribal prosecutor on the Standing Rock Reservation in North and South Dakota since 2009, said he doesn’t put a lot of stock into declination rates because he talks to federal prosecutors on a regular basis.

The DOJ’s declination rate includes cases referred to and prosecuted in tribal courts, where sentences can go beyond the traditional maximum penalty of one year in jail if certain provisions are met under federal law.

“Declinations aren’t really a big deal anymore to us because we know what the case is, and if the federal government declines we’ve already had a chance to prosecute that case too,” Walker said. “So it’s not like the ball is hidden, and the prosecution’s office doesn’t know about it.”

Purdon cited a drug trafficking case on the Standing Rock Reservation dubbed “Operation Prairie Thunder,” in which 12 people were indicted in federal and five in Standing Rock tribal court. Purdon said that while the tribal cases were subtracted from their prosecution record, it showed unprecedented cooperation and could lead to long-term success.

Former Standing Rock Tribal Judge Bill Zuger, who stepped down last year after six years on the bench, said that case was the product of federal prosecutors showing interest and building up trust with tribal law enforcement. Until recently, Zuger said he never had seen a U.S. attorney on the reservation.

“The people down there, anecdotally, feel that things are getting better,” Zuger said. “Keep in mind it took 125 years to screw it up. It takes a while to fix it. It’s going to take more than four or five years to really straighten out the mess.”