MADISON (AP) - A bill that would put outside agencies in charge of investigating officer-involved deaths could create conflict and confusion for Wisconsin agencies that have traditionally done it themselves, police observers say.

The measure's supporters say the new requirements will counter claims that police protect their own from consequences of using deadly force. The bill passed the Legislature earlier this year and Gov. Scott Walker has signaled he will sign it into law soon.

Most of Wisconsin's smaller law enforcement agencies already use outside investigators. But larger departments such as Green Bay, Madison and Milwaukee have investigated their own for years. Outsiders stepping into their affairs could be met with animosity.

"In general police departments don't like outsiders getting involved in their business, whether it be reporters, researchers or the community in general," said Steven Brandl, a University of Wisconsin-Milwaukee associate criminal justice professor.

Fifty-three people died while in the process of arrest in Wisconsin between 2003 and 2009, according to the latest figures from the U.S. Bureau of Justice Statistics. Wisconsin police departments reported officers killed 41 people between June 2008 and April 2013, according to the state Department of Justice. All the killings were ruled justifiable homicide.

Rep. Chris Taylor, D-Madison, and Rep. Garey Bies, R-Sister Bay, developed the legislation in response to three high-profile deaths in the last 10 years. They pointed to the deaths of Michael Bell, whom Kenosha police shot in the head as he fought with officers in 2004; robbery suspect Derek Williams, who died gasping for breath and begging for help in a Milwaukee squad car in 2011; and Paul Heenan, shot to death by a Madison officer during a scuffle in 2012.

None of those incidents resulted in criminal charges, raising questions from the dead men's families about the integrity of the investigations.

"The public should have confidence that the investigation was handled properly and without bias," Bies wrote to the Assembly criminal justice committee in December.

The bill would allow agencies to conduct internal investigations but they would also have to launch a criminal investigation involving at least two outside investigators. One of the outsiders must lead the criminal inquiry. The investigators would ultimately submit a report to the district attorney, who would make a charging decision.

Most smaller Wisconsin departments already rely on outside investigators because they lack manpower and want to avoid the appearance they're covering up for their own.

The bill would force larger, resource-rich agencies such as Green Bay, Madison and Milwaukee that have been investigating their own for years to give up control to outsiders. The measure is silent on how to set up agreements between agencies on who to call, when and how much training outsiders should have, creating logistical questions for agencies that have relied on themselves for decades.

"There's going to be a number of unknowns here," said Green Bay Police Lt. Chad Ramos. "We put together very transparent investigations. How is it we can't trust our own officers to investigate themselves?"

A Madison Police spokesman declined comment. Officials from that department, though, have joined a committee working to establish a pool of investigators that can work any officer-involved death in Dane County, said UW-Madison Police Chief Sue Riseling, the committee's chairwoman.

Milwaukee police already deal with a complex system for investigating officer-involved deaths. The city has a response team that includes the district attorney, the medical examiner and the police commission.

District Attorney John Chisholm said his office has charged only two officers in death incidents in about 40 years. DOJ data shows 14 of the 41 officer-involved homicides between 2008 and 2013 involved Milwaukee police but Chisholm himself hasn't charged any officers since he took over in 2007. Chisholm said the investigations have never generated evidence to support charges.

"No one has any problem being transparent. I just don't know that (the investigations) can be done any better than they are now," Milwaukee Police Association President Mike Crivello said. The association is the union for city officers.

State Rep. Evan Goyke, a Milwaukee Democrat and a former public defender who co-sponsored the bill, said it's difficult to believe not one officer did anything wrong.

"I respect that on paper we have all these procedures in place, but in practice they've come to these same conclusions that defy possibility," he said.

Chisholm said he doesn't charge people based on statistics. Regardless, Milwaukee law enforcement leaders started talking several weeks ago about establishing a team of investigators that can float around the county similar to Dane County's plans, he said.

The state Justice Department plans to develop a model policy police can follow to comply with the bill, agency spokeswoman Dana Brueck said. She couldn't elaborate any further because DOJ is still researching what the policy should include.

Walker hasn't publicly expressed any support for the bill. But he's also said he has no policy problems with any measures awaiting his signature.