A man convicted of killing four people in Northampton County is asking the U.S. Supreme Court to hear the case.

Michael Ballard pleaded guilty in March 2011 to the stabbing deaths in 2010 of his ex-girlfriend, Denise Mehri; her father, Dennis Marsh; and her grandfather, Alvin Marsh at their home in Northampton. Ballard also killed neighbor Steven Zernhelt, who heard cries and came over to help.

Ballard was given four death sentences, one for each victim.

The Pennsylvania Supreme Court denied to hear an appeal in November 2013.

Marc Bookman, executive director of the Philadelphia-based Atlantic Center for Capital Representation, filed papers asking the highest court to hear the case.

The appeal questions the legality of the Pennsylvania death penalty, saying the death penalty is unconstitutional because it doesn't mandate that 'non-statutory mitigating factors' be included on the verdict slip that's given to the jury.

Northampton County District Attorney John Morganelli told 69 News he's not overly concerned and doesn't think the U.S. Supreme Court will hear the case.

Morganelli said he'll file his response this week.