CHARLESTON, W.Va. -- A Charleston teenager convicted of killing an elderly neighbor plans to seek a reduced sentence.

Thomas Mallo will turn 18 in December and must begin serving a 40-year prison sentence.

Mallo has been held at the Industrial Home for Youth in Salem since he pleaded guilty in 2010 to second-degree murder. Prosecutors say he fatally stabbed 80-year-old Phyllis Jean Phares in 2009.

Mallo was 14 at the time of Phares' death.

Kanawha County Chief Public Defender George Castelle plans to ask a judge to reduce the sentence.

Kanawha County assistant prosecutor Maryclaire Akers says she'll oppose any reduction in Mallo's sentence.

Mallo also faces charges in Harrison County of attacking an officer and trying to escape from the Salem facility.