RALEIGH, N.C. — A Michigan State University law professor says she couldn't find anything in her data other than race to explain why potential black jurors are rejected more than twice as often by prosecutors for North Carolina death penalty trials compared to whites.

Barbara O'Brien spoke Tuesday to a House committee examining how to make changes to the 2009 Racial Justice Act, which allows a judge to decide whether race played a significant factor in someone's death sentence. The judge can then reduce the sentence to life in prison.

"We observed consistently large disparities at the rate prosecutors struck black jurors in capital cases compared to their counterparts," O'Brien told lawmakers.

O'Brien testified earlier this year at Marcus Robinson's Racial Justice Act hearing in Fayetteville – the first of its kind in the state – and presented the study she co-authored examining cases involving all 173 people on death row in 2010.

A judge has yet to rule on Marcus Robinson's appeal.

Robinson, 38, who is black, said race played a role in jury selection at his trial. He was sentenced to death in Cumberland County for the 1991 murder of a white 17-year-old, Erik Tornblom, who was driven into the woods, robbed and shot in the face with a sawed-off shotgun.

Almost all of the 157 people now on North Carolina's death row have filed appeals under the Racial Justice Act, even white inmates whose victims were also white.

Prosecutors say most of the appeals are frivolous, and they noted that the same death row data O'Brien used shows defense lawyers get rid of white jurors at a much higher rate than they strike black jurors.

"The interesting thing is, on the defense side, there's also a disparity," Jonathan Perry, an assistant district attorney in Union County, told lawmakers.

Prosecutors also argue that the law relies too much on numbers and not evidence in specific cases.

"The facts have to matter. If the facts don't matter, then really, what we're saying is just let the stats apply," Assistant Forsyth County District Attorney Mike Silver said.

Various legal challenges have put the death penalty on hold in North Carolina for almost six years.