He calls it his "nerd defense," and, indeed, African-American defendants wearing glasses are seen as more intelligent and honest, according to a 2008 study. (Glasses did not have the same effect with white defendants). It hasn't always worked: Slovis gave fake glasses to five African-American defendants on trial for a 2010 murder, but the prosecution figured out the scheme and branded the nerdy glasses as "masks."
The science shows that it works, too -- they did an experiment with two fake defendants, one white, one black. Both were photographed with and without glasses. More than 200 "jurors" were given one of the four pictures and told that the person in the picture was accused of snatching a woman's purse and cutting her face with a box cutter. Damn, scientists, that's ... weirdly specific. Anyway, in the experiment, adding glasses reduced the percentage of "guilty" verdicts by 20 percent. Note: This only works for violent crime. If you're accused of a white-collar nerd crime, the glasses lead to more guilty verdicts.