MEMPHIS, Tenn. -- A pile of stuffed animals marks the spot where 15-year-old Justin Thompson fell, fatally shot by an off-duty Memphis police officer on a school night in a working-class neighborhood.

The Sept. 24 shooting is still under investigation, but the question of whether Officer Terrance Shaw used excessive force makes the case one more example for critics who say there is a years-long culture of misconduct in the police department of Tennessee's largest city.

This year, at least 23 Memphis officers and civilian personnel have been charged with crimes, from DUI and drug dealing to human sex trafficking. Going back to 2004, dozens of officers in the 2,400-officer force have been charged with corruption.

Thompson's death was a tipping point for Mayor A C Wharton Jr. in recently ordering a review of the department by an outside group, like Miami, Los Angeles and other major cities with troubled departments have done in the past.

Wharton says the department's arrests are causing the public to lose faith in its police. Among the most shocking of the arrests this year was an officer charged with sex trafficking, accused of making a deal while on duty to take prostitutes to work at a party in Mississippi.

That officer was investigated and charged by the FBI's Tarnished Badge Task Force. It also investigated an officer charged with computer fraud and another charged with drug possession. Other officers have been charged this year with theft of property, felony shoplifting, domestic violence and DUI.

The call for an external investigation has put Police Director Toney Armstrong on the defensive. He says he's not resigning despite heavy public scrutiny.

Members of the community have held rallies decrying police corruption, saying they no longer trust the men and women charged with protecting them.

A group of church pastors – always an influential part of the Memphis community – has expressed support for the department and Armstrong, who has noted that the bad behavior of a few officers is tainting the actions of the entire force.

Community groups are trying to improve communication between residents and the police department. The Mid-South Peace & Justice Center is organizing meetings in which residents can talk directly with officers and voice their concerns.

"There are some who are angry, there are some who feel they are not being communicated with," said Melissa Miller-Monie, who organizes the Community-Police Relations project. "Some want answers. Some want changes in policies."

Even the cases that have not ended up in arrests have angered the community. An officer involved in a crash that killed two people in late August did not have his lights or sirens on, a violation of police policies.

"It appears that it's a systemic issue," said law enforcement consultant Melvin Tucker, who has served as police chief in four Southern cities. "It's a cultural problem more than likely. Something in the organization is allowing that to happen or not discouraging it."

Other cities major U.S. cities have faced similar problems and investigations hoping to solve them. After the Rodney King beating in 1991, Los Angeles Mayor Tom Bradley appointed lawyer Warren Christopher to lead a commission to investigate the city's police department. Christopher later became President Clinton's Secretary of State.

The Christopher Commission recommended stronger leadership, better screening of applicants, stronger training practices, and the creation of an inspector general position to oversee misconduct cases. It didn't prove to be a cure-all. In the late 1990s, the LAPD became mired in the Rampart corruption scandal with officers stealing drugs, framing gang members and committing extortion.

Wharton hasn't said which organization he would ask for the review, but experts have said that organizations like the International Association of Chiefs of Police or the Police Executive Research Forum would be good choices.

Wharton also has the option of asking the U.S. Justice Department for help. Since 2010, the Justice Department has reached agreements in Seattle, New Orleans and Warren, Ohio, to resolve complaints about misconduct in their police departments.

Tucker said whoever is brought in should look at whether the misconduct is taking place within certain divisions of the department and whether there's a system to identify officers with several complaints against them.

"That's the way that you prevent these things from turning into DUI's and sex trafficking and all that," Tucker said. "The answer is not always firing the police chief."

Shoring up hiring standards is a logical step. Miami's police department suffered serious problems after it lowered standards to raise the number of officers in the 1980s. The Miami River Cops were accused of robbing cocaine dealers of cash and drugs, and at least 20 were sentenced to prison. Hiring standards were raised after the scandal, and that helped reduce police corruption in Miami.

Recently, the Memphis City Council has discussed whether requiring a four-year undergraduate degree might slow the number of arrests.

The current requirement is two years of college or two years of military service, or at least three years at another department with at least 20 officers. Those requirements were reduced to a high school diploma or GED in 2008 but were reinstated in 2010.

Currently, the department does not use polygraph examinations in hiring. The practice could root out some potentially problematic officers, said Mike Hill, program manager at the University of Tennessee's Law Enforcement Innovation Center and a former officer in the suburb of Germantown.

Retired officer and law enforcement consultant Andrew Scott said Armstrong must be willing to set aside personal relationships developed over more than 20 years of serving in the Memphis Police Department and be willing to discipline officers or supervisors he knows well.

Armstrong, a Memphis native, was promoted to police director in April 2011.

"The question begs: Can he and will he have the ability and the strength and the fortitude to do what needs to be done to remove people from office and replace them with competent people?" Scott said.

Meanwhile, Shirley Thompson waits for answers. She wants to know why an off-duty officer would shoot her son. Authorities say Officer Shaw was a victim of an armed robbery that ended in the teen's shooting, but few other details have been released.

The Tennessee Bureau of Investigation, asked to probe the shooting, has several questions to answer, including what Thompson's involvement was in the robbery and if Shaw used excessive force in shooting Thompson.

Shirley Thompson and other relatives say her son's Facebook page, which had photos of him flashing gang signs, fanning out cash, and making statements about his involvement in street life, are not an accurate portrayal of her son. She believes her son did not rob anybody.

"I'm just waiting on the truth," she said during a candlelight vigil for her son. "I'm just staying strong for my son. I'm looking for the mayor to give me the truth."

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