COLUMBIA, S.C. (AP) — Republican presidential candidate Ben Carson told a group of African-American civic leaders on Saturday that he is still waiting to see evidence of racial bias by law enforcement agencies in the U.S.
The only major White House hopeful who is black, Carson also mused during a criminal justice forum that he never had problems with police as a young black male in Detroit "because I was taught by my mother to be very respectful of authority."
Carson later demurred when pressed on whether he could offer examples of "institutional racism" in America. "It probably exists somewhere," he said. "If it exists, expose it. ... That's your best defense."
The forum, also attended by Democratic candidates Bernie Sanders and Martin O'Malley, was sponsored by the 20/20 Club, a bipartisan group of African-American civic, business and political leaders formed as an alternative to the Black Lives Matter movement. Organizers say their purpose is to press candidates on their ideas for addressing a criminal justice system that disproportionately imprisons minorities and the poor.
Click through images of Ben Carson on the campaign trail:
Ben Carson on the campaign trail
Carson questions claims of racial bias against police
Republican presidential candidate Dr. Ben Carson gestures while speaking during a town hall at Abundant Life Ministries in Jefferson, Iowa, Monday, Jan. 11, 2016. (AP Photo/Patrick Semansky)
MT. AYR, IA - JANUARY 22 : Republican presidential candidate Ben Carson is introduced during his 'Trust in God Townhall' campaign stop January 22, 2016 in Mt. Ayr, Iowa. Carson, who is seeking the nomination from the Republican Party is on the presidential campaign trail across Iowa ahead of the Iowa Caucus taking place February 1. (Photo by Joshua Lott/Getty Images)
Republican presidential candidate Dr. Ben Carson walks through the National Motorcycle Museum in Anamosa, Iowa, Thursday, Jan. 7, 2016, after holding a town hall. (AP Photo/Patrick Semansky)
Republican presidential candidate Dr. Ben Carson smiles during an interview with The Associated Press in his home in Upperco, Md., Wednesday, Dec. 23, 2015. (AP Photo/Andrew Harnik)
Republican presidential candidate Dr. Ben Carson speaks during a campaign event at Cobb Energy Center Tuesday, Dec. 8, 2015, in Atlanta. (AP Photo/David Goldman)
Republican presidential candidate, Dr. Ben Carson speaks during a town hall meeting at Winthrop University on Wednesday, Dec. 2, 2015, in Rock Hill, S.C. (AP Photo/Rainier Ehrhardt)
Republican presidential candidate Dr. Ben Carson speaks at a rally Sunday, Nov. 15, 2015, in Henderson, Nev. (AP Photo/John Locher)
Ben Carson, 2016 Republican presidential candidate, speaks during a Liberty University Convocation in Lynchburg, Virginia, U.S., on Wednesday, Nov. 11, 2015. As retired neurosurgeon Carson has risen in the polls, media reports have revisited his accounts of acts of violence as a child, a key part of the redemption story he discusses on the campaign trail. Photographer: Andrew Harrer/Bloomberg via Getty Images
PALM BEACH GARDENS, FL - NOVEMBER 06: Republican presidential candidate Ben Carson speaks to the media before speaking at a gala for the Black Republican Caucus of South Florida at PGA National Resort on November 6, 2015 in Palm Beach, Florida. Carson has come under media scrutiny for possibly exaggerating his background and other statements he has made recently. (Photo by Joe Raedle/Getty Images)
Republican presidential candidate Ben Carson greets well-wishers during a campaign stop, Thursday, Oct. 29, 2015, in Lakewood, Colo. (AP Photo/David Zalubowski)
DES MOINES, IA - AUGUST 16: Republican presidential hopeful Ben Carson (L) eats a piece of pizza while touring the Iowa State Fair on August 16, 2015 in Des Moines, Iowa. Presidential candidates are addressing attendees at the Iowa State Fair on the Des Moines Register Presidential Soapbox stage and touring the fairgrounds. The State Fair runs through August 23. (Photo by Justin Sullivan/Getty Images)
Republican presidential candidate Ben Carson speaks during a campaign stop, Thursday, Oct. 29, 2015, in Lakewood, Colo. (AP Photo/David Zalubowski)
FILE - In this Oct. 24, 2015, file photo, Republican presidential candidate Dr. Ben Carson greets audience members after speaking at Iowa State University in Ames, Iowa. Seven in 10 Republican and Republican-leaning registered voters say Donald Trump could win the November 2016 election. That compares to 6 in 10 who say the same for retired neurosurgeon Carson, who, like Trump, has tapped into the powerful wave of anti-establishment anger defining the early phases of the 2016 contest. (AP Photo/Charlie Neibergall, File)
LAKEWOOD, CO - OCTOBER 29: Republican presidential candidate Ben Carson speaks during a news conference before a campaign event at Colorado Christian University on October 29, 2015 in Lakewood, Colorado. Ben Carson was back on the campaign trail a day after the third republican debate held at the University of Colorado Boulder. (Photo by Justin Sullivan/Getty Images)
Republican presidential candidate Dr. Ben Carson speaks outside the Alpha Gamma Rho fraternity at Iowa State University during a campaign stop, Saturday, Oct. 24, 2015, in Ames, Iowa. (AP Photo/Charlie Neibergall)
Republican presidential candidate Dr. Ben Carson, left, laughs as he wife, Candy Carson, waves to the crowd after saying a few words to the crowd supporting her husband in front of supporters Tuesday, Aug. 18, 2015, in Phoenix. (AP Photo/Ross D. Franklin)
Republican presidential candidate Dr. Ben Carson greets audience members following a town hall meeting, Friday, Oct. 2, 2015, in Ankeny, Iowa. (AP Photo/Charlie Neibergall)
Republican presidential candidate Dr. Ben Carson speaks at a luncheon at the National Press Club in Washington, Friday, Oct. 9, 2015. Carson is promoting a book he has co-authored with his wife Candy Carson entitled 'A More Perfect Union: What We the People Can Do to Reclaim Our Constitutional Liberties.' (AP Photo/Andrew Harnik)
WASHINGTON, DC - SEPTEMBER 25: Scenes around the the Value Voters Summit on September 25, 2015 in Washington DC. Republican presidential candidate Ben Carson takes the stage at the event. Dr Carson speaks to the media after the speach. (Photos by Charles Ommanney/The Washington Post via Getty Images)
Attendees wait for Ben Carson, 2016 Republican presidential candidate, not pictured, to arrive during a campaign stop at the birthplace of the Michigan Republican Party in Jackson, Michigan, U.S., on Wednesday, Sept. 23, 2015. Carson, the third candidate in the Republican race to have never held elected office, saw his numbers drop following the debate last week. Photographer: Luke Sharrett/Bloomberg via Getty Images
Republican presidential candidate Ben Carson speaks at a presidential forum sponsored by Heritage Action at the Bon Secours Wellness Arena, Friday, Sept. 18, 2015, in Greenville, S.C. (AP Photo/Richard Shiro)
Republican Presidential candidate Dr. Ben Carson during a speech to the Commonwealth Club public affairs forum Tuesday, Sept. 8, 2015, in San Francisco. (AP Photo/Eric Risberg)
Republican presidential candidate Ben Carson speaks at a rally in Little Rock, Ark., Thursday, Aug. 27, 2015. (AP Photo/Danny Johnston)
Republican presidential candidate Ben Carson is interviewed in Little Rock, Ark., Thursday, Aug. 27, 2015. (AP Photo/Danny Johnston)
Republican presidential candidate Ben Carson stands for a photo with a fairgoer at the Iowa State Fair Sunday, Aug. 16, 2015, in Des Moines. (AP Photo/Charlie Riedel)
Ben Carson, 2016 Republican presidential candidate, listens as he attends a service at Maple Street Missionary Baptist Church in Des Moines, Iowa, U.S., on Sunday, Aug. 16, 2015. Carson will be speaking at the Iowa State Fair, which is expected to host 18 presidential candidates and runs until Aug. 23. Photographer: Daniel Acker/Bloomberg via Getty Images
Republican presidential candidate Dr. Ben Carson speaks to hundreds of supporters at the Inaugural Basque Fry at Corley Ranch in Gardnerville, Nev. on Saturday, Aug. 15, 2015. (AP Photo/Lance Iversen)
CLEVELAND, OH - AUGUST 06: Republican presidential candidate Ben Carson participates in the first prime-time presidential debate hosted by FOX News and Facebook at the Quicken Loans Arena August 6, 2015 in Cleveland, Ohio. The top-ten GOP candidates were selected to participate in the debate based on their rank in an average of the five most recent national political polls. (Photo by Chip Somodevilla/Getty Images)
Republican presidential candidate, retired neurosurgeon Ben Carson, speaks at the Family Leadership Summit in Ames, Iowa, Saturday, July 18, 2015. (AP Photo/Nati Harnik)
Republican presidential candidate, retired neurosurgeon Ben Carson, right, speaks with pollster Frank Luntz at the Family Leadership Summit in Ames, Iowa, Saturday, July 18, 2015. (AP Photo/Nati Harnik)
Ben Carson, 2016 Republican presidential candidate, eats a slice of pizza as he tours the Iowa State Fair in Des Moines, Iowa, U.S., on Sunday, Aug. 16, 2015. In a Sunday interview with Fox News, Carson doubled down on his assertion that a speech given by President Barack Obama intended to sell the American public on his nuclear deal with Iran contained 'coded innuendos employing standard anti-Semitic themes.' Photographer: Daniel Acker/Bloomberg via Getty Images
Republican presidential candidate Ben Carson speaks at the National Sheriffsâ Association presidential forum, Tuesday, June 30, 2015, in Baltimore. (AP Photo/Patrick Semansky)
Republican presidential candidate Dr. Ben Carson is greeted by supporters during a fundraiser for U.S. Sen. Joni Ernst, R-Iowa, Saturday, June 6, 2015, in Boone, Iowa. (AP Photo/Charlie Neibergall)
Republican presidential hopeful Sen. Rand Paul, left, talks with Republican presidential hopeful Dr. Ben Carson during the Iowa Republican Party's Lincoln Dinner, Saturday, May 16, 2015, in Des Moines, Iowa. (AP Photo/Charlie Neibergall)
Republican presidential candidate and retired neurosurgeon Ben Carson speaks at Manchester Community College, Sunday, May 10, 2015, in Manchester, N.H. (AP Photo/Mary Schwalm)
Republican presidential candidate Ben Carson speaks in town hall meeting in Baltimore Md., Thursday May 7, 2015. (AP Photo/Jose Luis Magana)
Ben Carson announces his candidacy for president during an official announcement in Detroit, Monday, May 4, 2015. Carson, 63, a retired neurosurgeon, begins the Republican primary as an underdog in a campaign expected to feature several seasoned politicians. (Photo/Paul Sancya)
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Carson, who is at or near the top of several GOP presidential preference polls, made his remarks in response to questions about high-profile cases of alleged police misconduct, including several where African-Americans were either killed by police or died in custody.
The retired neurosurgeon told moderator Jeffrey Johnson of the Black Entertainment Television network, "I'm not aware of a lot of cases where a police officer just comes up to somebody like you and says, 'Hey, I don't like you. I'm going to shoot you."
Carson continued, "I'm still waiting for the evidence."
Johnson retorted, "I'll show you the Tamir Rice tape." He drew applause from the forum audience with the reference to the 12-year-old Ohio boy who was shown on video being shot and killed last year by a Cleveland police officer. The case is expected to go a grand jury in the coming weeks.
Carson later explained that he believes a "rogue policeman" should be "punished to the fullest extent of the law." But he said changing public policy "based on bad apples ... will always lead you into an area of unnecessary conflict."
Unlike Carson, Sanders and O'Malley — both of whom have had run-ins with protesters from Black Lives Matter — emphasized their disgust with the deaths of black citizens at the hands of police officers.
O'Malley said the worst aspects of the U.S. criminal justice system traces itself back to slavery. Sanders said overhauling police practices should be the first step in criminal justice reform that he framed as "the civil rights issue of the 21st century."
Sanders called for federal aid to help local law enforcement agencies with better training programs, while also "demilitarizing" police forces and withholding federal money from agencies that don't comply with new standards.
Each of the three candidates endorsed "community policing," a concept that calls for assigning officers to specific communities or neighborhoods so they can establish trust with residents. Each rejected mandatory minimum sentences, laws that require judges to hand down specific sentences for certain charges.
They also called for restoring voting rights to felons who have completed their sentences, a position that separates Carson from some of his GOP rivals.
Carson also joined his Democratic counterparts in endorsing calls for treating more drug offenders for addiction, rather than incarcerating them. But Sanders went further, repeating his call to decriminalize marijuana at the federal level.
The trio agreed generally that poverty and a lack of educational opportunity are among the root causes of drug use and crime.
Yet Carson and Sanders, in particular, diverged widely in how to change course. Carson argued for encouraging more private sector investment in the economy through tax incentives, while Sanders pitched several of his familiar proposals, such as making public colleges tuition-free.