AURORA, Ill. (CBS) — Gareng Deng remains behind bars for the murder of Marilyn Bethell six years ago, but her friends wonder who else should be.

As WBBM Newsradio’s Nancy Harty reports, last month, Kane County Judge Allen Anderson denied Deng’s request to withdraw his guilty plea in the murder of Bethell, a 47-year-old substance abuse counselor, in Aurora in 2005.

LISTEN: WBBM Newsradio’s Nancy Harty reports

But friends of Bethell’s tell the Chicago Tribune if the case had gone to trial, they might have gotten some answers, including who the driver was who picked up Deng after he crashed Bethell’s car the day after she was last seen alive.

Deng, 20, tells the Tribune he was there when Bethell died, but he didn’t pull the trigger. He will not name his accomplice, but denies the man is in his gang or a relative, the Tribune reported.

Deng was 17 when he pleaded guilty to the murder in 2009, and was sentenced to 35 years in prison.