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(The Root) -- The U.S. Commission on Civil Rights announced on Friday that it will launch a special investigation into "Stand your ground" laws and whether racial bias plays a role in how they are enforced. The legislation -- which allows people to use deadly force, without any obligation to retreat first, when they believe they are being seriously threatened -- gained national attention this year after the shooting of Trayvon Martin. In that case, Florida police initially cited the statute as George Zimmerman’s legal defense in killing the unarmed teenager.

While at least 21 states have some form of the law on the books, there is little data on how they have been applied across the country. The eight-member bipartisan commission plans to gather such data as they hold hearings and interview law-enforcement officials nationwide. According to the commission:

Data compiled by the Wall Street Journal shows a near-doubling of justifiable homicides from 2005-2011 in states where SYG [Stand Your Ground] passed. Moreover, their data shows that while white killers of black victims comprises only 3.1% of all homicides, such cross-racial killings constitute 15.6% of justifiable homicides.

Also, an advisory group to the National District Attorneys Association met in 2007 and issued a report that, in part, concluded that among the "negative consequences" of SYG-type legislation were "a misinterpretation of physical clues that results in the use of deadly force, exacerbating culture, class, and race differences," and "a disproportionately negative effect on minorities, persons from lower socio-economic status, and young adults/juveniles."

There is also a general body of social science research that has examined the effects of race on the perception of threat and even split-second decisions on whether to fire a gun. However, the implications of this social science research for justifiable homicides subject to SYG laws have not been carefully studied. A fact-based, systematic review is needed of SYG laws and their implementation.

In the 5-3 vote on whether they should review "Stand your ground" legislation, all four Democrats on the panel, and one Republican, voted in favor of an investigation. The commission plans to release its findings within one year.

Cynthia Gordy is The Root's senior political correspondent.

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